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Publisher: John Wiley and Sons   (Total: 1589 journals)

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Showing 1 - 200 of 1589 Journals sorted alphabetically
Abacus     Hybrid Journal   (Followers: 12, SJR: 0.48, h-index: 22)
About Campus     Hybrid Journal   (Followers: 5)
Academic Emergency Medicine     Hybrid Journal   (Followers: 65, SJR: 1.385, h-index: 91)
Accounting & Finance     Hybrid Journal   (Followers: 48, SJR: 0.547, h-index: 30)
ACEP NOW     Free   (Followers: 1)
Acta Anaesthesiologica Scandinavica     Hybrid Journal   (Followers: 53, SJR: 1.02, h-index: 88)
Acta Archaeologica     Hybrid Journal   (Followers: 168, SJR: 0.101, h-index: 9)
Acta Geologica Sinica (English Edition)     Hybrid Journal   (Followers: 3, SJR: 0.552, h-index: 41)
Acta Neurologica Scandinavica     Hybrid Journal   (Followers: 5, SJR: 1.203, h-index: 74)
Acta Obstetricia et Gynecologica Scandinavica     Hybrid Journal   (Followers: 15, SJR: 1.197, h-index: 81)
Acta Ophthalmologica     Hybrid Journal   (Followers: 6, SJR: 0.112, h-index: 1)
Acta Paediatrica     Hybrid Journal   (Followers: 56, SJR: 0.794, h-index: 88)
Acta Physiologica     Hybrid Journal   (Followers: 6, SJR: 1.69, h-index: 88)
Acta Polymerica     Hybrid Journal   (Followers: 9)
Acta Psychiatrica Scandinavica     Hybrid Journal   (Followers: 37, SJR: 2.518, h-index: 113)
Acta Zoologica     Hybrid Journal   (Followers: 7, SJR: 0.459, h-index: 29)
Acute Medicine & Surgery     Hybrid Journal   (Followers: 5)
Addiction     Hybrid Journal   (Followers: 36, SJR: 2.086, h-index: 143)
Addiction Biology     Hybrid Journal   (Followers: 14, SJR: 2.091, h-index: 57)
Adultspan J.     Hybrid Journal   (SJR: 0.127, h-index: 4)
Advanced Energy Materials     Hybrid Journal   (Followers: 26, SJR: 6.411, h-index: 86)
Advanced Engineering Materials     Hybrid Journal   (Followers: 26, SJR: 0.81, h-index: 81)
Advanced Functional Materials     Hybrid Journal   (Followers: 51, SJR: 5.21, h-index: 203)
Advanced Healthcare Materials     Hybrid Journal   (Followers: 14, SJR: 0.232, h-index: 7)
Advanced Materials     Hybrid Journal   (Followers: 295, SJR: 9.021, h-index: 345)
Advanced Materials Interfaces     Hybrid Journal   (Followers: 6, SJR: 1.177, h-index: 10)
Advanced Optical Materials     Hybrid Journal   (Followers: 7, SJR: 2.488, h-index: 21)
Advanced Science     Open Access   (Followers: 5)
Advanced Synthesis & Catalysis     Hybrid Journal   (Followers: 17, SJR: 2.729, h-index: 121)
Advances in Polymer Technology     Hybrid Journal   (Followers: 13, SJR: 0.344, h-index: 31)
Africa Confidential     Hybrid Journal   (Followers: 21)
Africa Research Bulletin: Economic, Financial and Technical Series     Hybrid Journal   (Followers: 13)
Africa Research Bulletin: Political, Social and Cultural Series     Hybrid Journal   (Followers: 11)
African Development Review     Hybrid Journal   (Followers: 33, SJR: 0.275, h-index: 17)
African J. of Ecology     Hybrid Journal   (Followers: 16, SJR: 0.477, h-index: 39)
Aggressive Behavior     Hybrid Journal   (Followers: 15, SJR: 1.391, h-index: 66)
Aging Cell     Open Access   (Followers: 11, SJR: 4.374, h-index: 95)
Agribusiness : an Intl. J.     Hybrid Journal   (Followers: 3, SJR: 0.627, h-index: 14)
Agricultural and Forest Entomology     Hybrid Journal   (Followers: 16, SJR: 0.925, h-index: 43)
Agricultural Economics     Hybrid Journal   (Followers: 45, SJR: 1.099, h-index: 51)
AIChE J.     Hybrid Journal   (Followers: 32, SJR: 1.122, h-index: 120)
Alcoholism and Drug Abuse Weekly     Hybrid Journal   (Followers: 7)
Alcoholism Clinical and Experimental Research     Hybrid Journal   (Followers: 7, SJR: 1.416, h-index: 125)
Alimentary Pharmacology & Therapeutics     Hybrid Journal   (Followers: 33, SJR: 2.833, h-index: 138)
Alimentary Pharmacology & Therapeutics Symposium Series     Hybrid Journal   (Followers: 3)
Allergy     Hybrid Journal   (Followers: 51, SJR: 3.048, h-index: 129)
Alternatives to the High Cost of Litigation     Hybrid Journal   (Followers: 3)
American Anthropologist     Hybrid Journal   (Followers: 152, SJR: 0.951, h-index: 61)
American Business Law J.     Hybrid Journal   (Followers: 24, SJR: 0.205, h-index: 17)
American Ethnologist     Hybrid Journal   (Followers: 93, SJR: 2.325, h-index: 51)
American J. of Economics and Sociology     Hybrid Journal   (Followers: 29, SJR: 0.211, h-index: 26)
American J. of Hematology     Hybrid Journal   (Followers: 35, SJR: 1.761, h-index: 77)
American J. of Human Biology     Hybrid Journal   (Followers: 13, SJR: 1.018, h-index: 58)
American J. of Industrial Medicine     Hybrid Journal   (Followers: 16, SJR: 0.993, h-index: 85)
American J. of Medical Genetics Part A     Hybrid Journal   (Followers: 16, SJR: 1.115, h-index: 61)
American J. of Medical Genetics Part B: Neuropsychiatric Genetics     Hybrid Journal   (Followers: 4, SJR: 1.771, h-index: 107)
American J. of Medical Genetics Part C: Seminars in Medical Genetics     Partially Free   (Followers: 6, SJR: 2.315, h-index: 79)
American J. of Physical Anthropology     Hybrid Journal   (Followers: 37, SJR: 1.41, h-index: 88)
American J. of Political Science     Hybrid Journal   (Followers: 290, SJR: 5.101, h-index: 114)
American J. of Primatology     Hybrid Journal   (Followers: 16, SJR: 1.197, h-index: 63)
American J. of Reproductive Immunology     Hybrid Journal   (Followers: 3, SJR: 1.347, h-index: 75)
American J. of Transplantation     Hybrid Journal   (Followers: 18, SJR: 2.792, h-index: 140)
American J. on Addictions     Hybrid Journal   (Followers: 9, SJR: 0.843, h-index: 57)
Anaesthesia     Hybrid Journal   (Followers: 138, SJR: 1.404, h-index: 88)
Analyses of Social Issues and Public Policy     Hybrid Journal   (Followers: 9, SJR: 0.397, h-index: 18)
Analytic Philosophy     Hybrid Journal   (Followers: 20)
Anatomia, Histologia, Embryologia: J. of Veterinary Medicine Series C     Hybrid Journal   (Followers: 3, SJR: 0.295, h-index: 27)
Anatomical Sciences Education     Hybrid Journal   (Followers: 1, SJR: 0.633, h-index: 24)
Andrologia     Hybrid Journal   (Followers: 2, SJR: 0.528, h-index: 45)
Andrology     Hybrid Journal   (Followers: 2, SJR: 0.979, h-index: 14)
Angewandte Chemie     Hybrid Journal   (Followers: 179)
Angewandte Chemie Intl. Edition     Hybrid Journal   (Followers: 229, SJR: 6.229, h-index: 397)
Animal Conservation     Hybrid Journal   (Followers: 41, SJR: 1.576, h-index: 62)
Animal Genetics     Hybrid Journal   (Followers: 8, SJR: 0.957, h-index: 67)
Animal Science J.     Hybrid Journal   (Followers: 6, SJR: 0.569, h-index: 24)
Annalen der Physik     Hybrid Journal   (Followers: 5, SJR: 1.46, h-index: 40)
Annals of Anthropological Practice     Partially Free   (Followers: 2, SJR: 0.187, h-index: 5)
Annals of Applied Biology     Hybrid Journal   (Followers: 7, SJR: 0.816, h-index: 56)
Annals of Clinical and Translational Neurology     Open Access   (Followers: 1)
Annals of Human Genetics     Hybrid Journal   (Followers: 9, SJR: 1.191, h-index: 67)
Annals of Neurology     Hybrid Journal   (Followers: 48, SJR: 5.584, h-index: 241)
Annals of Noninvasive Electrocardiology     Hybrid Journal   (Followers: 1, SJR: 0.531, h-index: 38)
Annals of Public and Cooperative Economics     Hybrid Journal   (Followers: 8, SJR: 0.336, h-index: 23)
Annals of the New York Academy of Sciences     Hybrid Journal   (Followers: 5, SJR: 2.389, h-index: 189)
Annual Bulletin of Historical Literature     Hybrid Journal   (Followers: 13)
Annual Review of Information Science and Technology     Hybrid Journal   (Followers: 14)
Anthropology & Education Quarterly     Hybrid Journal   (Followers: 25, SJR: 0.72, h-index: 31)
Anthropology & Humanism     Hybrid Journal   (Followers: 17, SJR: 0.137, h-index: 3)
Anthropology News     Hybrid Journal   (Followers: 15)
Anthropology of Consciousness     Hybrid Journal   (Followers: 11, SJR: 0.172, h-index: 5)
Anthropology of Work Review     Hybrid Journal   (Followers: 11, SJR: 0.256, h-index: 5)
Anthropology Today     Hybrid Journal   (Followers: 91, SJR: 0.545, h-index: 15)
Antipode     Hybrid Journal   (Followers: 50, SJR: 2.212, h-index: 69)
Anz J. of Surgery     Hybrid Journal   (Followers: 8, SJR: 0.432, h-index: 59)
Anzeiger für Schädlingskunde     Hybrid Journal   (Followers: 1)
Apmis     Hybrid Journal   (Followers: 1, SJR: 0.855, h-index: 73)
Applied Cognitive Psychology     Hybrid Journal   (Followers: 70, SJR: 0.754, h-index: 69)
Applied Organometallic Chemistry     Hybrid Journal   (Followers: 7, SJR: 0.632, h-index: 58)
Applied Psychology     Hybrid Journal   (Followers: 209, SJR: 1.023, h-index: 64)
Applied Psychology: Health and Well-Being     Hybrid Journal   (Followers: 50, SJR: 0.868, h-index: 13)
Applied Stochastic Models in Business and Industry     Hybrid Journal   (Followers: 5, SJR: 0.613, h-index: 24)
Aquaculture Nutrition     Hybrid Journal   (Followers: 14, SJR: 1.025, h-index: 55)
Aquaculture Research     Hybrid Journal   (Followers: 32, SJR: 0.807, h-index: 60)
Aquatic Conservation Marine and Freshwater Ecosystems     Hybrid Journal   (Followers: 36, SJR: 1.047, h-index: 57)
Arabian Archaeology and Epigraphy     Hybrid Journal   (Followers: 11, SJR: 0.453, h-index: 11)
Archaeological Prospection     Hybrid Journal   (Followers: 12, SJR: 0.922, h-index: 21)
Archaeology in Oceania     Hybrid Journal   (Followers: 13, SJR: 0.745, h-index: 18)
Archaeometry     Hybrid Journal   (Followers: 29, SJR: 0.809, h-index: 48)
Archeological Papers of The American Anthropological Association     Hybrid Journal   (Followers: 15, SJR: 0.156, h-index: 2)
Architectural Design     Hybrid Journal   (Followers: 26, SJR: 0.261, h-index: 9)
Archiv der Pharmazie     Hybrid Journal   (Followers: 3, SJR: 0.628, h-index: 43)
Archives of Drug Information     Hybrid Journal   (Followers: 5)
Archives of Insect Biochemistry and Physiology     Hybrid Journal   (SJR: 0.768, h-index: 54)
Area     Hybrid Journal   (Followers: 13, SJR: 0.938, h-index: 57)
Art History     Hybrid Journal   (Followers: 274, SJR: 0.153, h-index: 13)
Arthritis & Rheumatology     Hybrid Journal   (Followers: 54, SJR: 1.984, h-index: 20)
Arthritis Care & Research     Hybrid Journal   (Followers: 27, SJR: 2.256, h-index: 114)
Artificial Organs     Hybrid Journal   (Followers: 1, SJR: 0.872, h-index: 60)
ASHE Higher Education Reports     Hybrid Journal   (Followers: 15)
Asia & the Pacific Policy Studies     Open Access   (Followers: 16)
Asia Pacific J. of Human Resources     Hybrid Journal   (Followers: 326, SJR: 0.494, h-index: 19)
Asia Pacific Viewpoint     Hybrid Journal   (Followers: 1, SJR: 0.616, h-index: 26)
Asia-Pacific J. of Chemical Engineering     Hybrid Journal   (Followers: 8, SJR: 0.345, h-index: 20)
Asia-pacific J. of Clinical Oncology     Hybrid Journal   (Followers: 6, SJR: 0.554, h-index: 14)
Asia-Pacific J. of Financial Studies     Hybrid Journal   (SJR: 0.241, h-index: 7)
Asia-Pacific Psychiatry     Hybrid Journal   (Followers: 4, SJR: 0.377, h-index: 7)
Asian Economic J.     Hybrid Journal   (Followers: 8, SJR: 0.234, h-index: 21)
Asian Economic Policy Review     Hybrid Journal   (Followers: 4, SJR: 0.196, h-index: 12)
Asian J. of Control     Hybrid Journal   (SJR: 0.862, h-index: 34)
Asian J. of Endoscopic Surgery     Hybrid Journal   (Followers: 1, SJR: 0.394, h-index: 7)
Asian J. of Organic Chemistry     Hybrid Journal   (Followers: 6, SJR: 1.443, h-index: 19)
Asian J. of Social Psychology     Hybrid Journal   (Followers: 5, SJR: 0.665, h-index: 37)
Asian Politics and Policy     Hybrid Journal   (Followers: 12, SJR: 0.207, h-index: 7)
Asian Social Work and Policy Review     Hybrid Journal   (Followers: 5, SJR: 0.318, h-index: 5)
Asian-pacific Economic Literature     Hybrid Journal   (Followers: 5, SJR: 0.168, h-index: 15)
Assessment Update     Hybrid Journal   (Followers: 4)
Astronomische Nachrichten     Hybrid Journal   (Followers: 3, SJR: 0.701, h-index: 40)
Atmospheric Science Letters     Open Access   (Followers: 29, SJR: 1.332, h-index: 27)
Austral Ecology     Hybrid Journal   (Followers: 15, SJR: 1.095, h-index: 66)
Austral Entomology     Hybrid Journal   (Followers: 9, SJR: 0.524, h-index: 28)
Australasian J. of Dermatology     Hybrid Journal   (Followers: 8, SJR: 0.714, h-index: 40)
Australasian J. On Ageing     Hybrid Journal   (Followers: 6, SJR: 0.39, h-index: 22)
Australian & New Zealand J. of Statistics     Hybrid Journal   (Followers: 14, SJR: 0.275, h-index: 28)
Australian Accounting Review     Hybrid Journal   (Followers: 3, SJR: 0.709, h-index: 14)
Australian and New Zealand J. of Family Therapy (ANZJFT)     Hybrid Journal   (Followers: 3, SJR: 0.382, h-index: 12)
Australian and New Zealand J. of Obstetrics and Gynaecology     Hybrid Journal   (Followers: 47, SJR: 0.814, h-index: 49)
Australian and New Zealand J. of Public Health     Hybrid Journal   (Followers: 11, SJR: 0.82, h-index: 62)
Australian Dental J.     Hybrid Journal   (Followers: 6, SJR: 0.482, h-index: 46)
Australian Economic History Review     Hybrid Journal   (Followers: 6, SJR: 0.171, h-index: 12)
Australian Economic Papers     Hybrid Journal   (Followers: 31, SJR: 0.23, h-index: 9)
Australian Economic Review     Hybrid Journal   (Followers: 6, SJR: 0.357, h-index: 21)
Australian Endodontic J.     Hybrid Journal   (Followers: 3, SJR: 0.513, h-index: 24)
Australian J. of Agricultural and Resource Economics     Hybrid Journal   (Followers: 3, SJR: 0.765, h-index: 36)
Australian J. of Grape and Wine Research     Hybrid Journal   (Followers: 5, SJR: 0.879, h-index: 56)
Australian J. of Politics & History     Hybrid Journal   (Followers: 15, SJR: 0.203, h-index: 14)
Australian J. of Psychology     Hybrid Journal   (Followers: 18, SJR: 0.384, h-index: 30)
Australian J. of Public Administration     Hybrid Journal   (Followers: 419, SJR: 0.418, h-index: 29)
Australian J. of Rural Health     Hybrid Journal   (Followers: 5, SJR: 0.43, h-index: 34)
Australian Occupational Therapy J.     Hybrid Journal   (Followers: 72, SJR: 0.59, h-index: 29)
Australian Psychologist     Hybrid Journal   (Followers: 12, SJR: 0.331, h-index: 31)
Australian Veterinary J.     Hybrid Journal   (Followers: 23, SJR: 0.459, h-index: 45)
Autism Research     Hybrid Journal   (Followers: 36, SJR: 2.126, h-index: 39)
Autonomic & Autacoid Pharmacology     Hybrid Journal   (SJR: 0.371, h-index: 29)
Banks in Insurance Report     Hybrid Journal   (Followers: 1)
Basic & Clinical Pharmacology & Toxicology     Hybrid Journal   (Followers: 11, SJR: 0.539, h-index: 70)
Basic and Applied Pathology     Open Access   (Followers: 2, SJR: 0.113, h-index: 4)
Basin Research     Hybrid Journal   (Followers: 5, SJR: 1.54, h-index: 60)
Bauphysik     Hybrid Journal   (Followers: 2, SJR: 0.194, h-index: 5)
Bauregelliste A, Bauregelliste B Und Liste C     Hybrid Journal  
Bautechnik     Hybrid Journal   (Followers: 1, SJR: 0.321, h-index: 11)
Behavioral Interventions     Hybrid Journal   (Followers: 9, SJR: 0.297, h-index: 23)
Behavioral Sciences & the Law     Hybrid Journal   (Followers: 24, SJR: 0.736, h-index: 57)
Berichte Zur Wissenschaftsgeschichte     Hybrid Journal   (Followers: 10, SJR: 0.11, h-index: 5)
Beton- und Stahlbetonbau     Hybrid Journal   (Followers: 2, SJR: 0.493, h-index: 14)
Biochemistry and Molecular Biology Education     Hybrid Journal   (Followers: 6, SJR: 0.311, h-index: 26)
Bioelectromagnetics     Hybrid Journal   (Followers: 1, SJR: 0.568, h-index: 64)
Bioengineering & Translational Medicine     Open Access  
BioEssays     Hybrid Journal   (Followers: 10, SJR: 3.104, h-index: 155)
Bioethics     Hybrid Journal   (Followers: 14, SJR: 0.686, h-index: 39)
Biofuels, Bioproducts and Biorefining     Hybrid Journal   (Followers: 1, SJR: 1.725, h-index: 56)
Biological J. of the Linnean Society     Hybrid Journal   (Followers: 16, SJR: 1.172, h-index: 90)
Biological Reviews     Hybrid Journal   (Followers: 5, SJR: 6.469, h-index: 114)
Biologie in Unserer Zeit (Biuz)     Hybrid Journal   (Followers: 41, SJR: 0.12, h-index: 1)
Biology of the Cell     Full-text available via subscription   (Followers: 9, SJR: 1.812, h-index: 69)
Biomedical Chromatography     Hybrid Journal   (Followers: 6, SJR: 0.572, h-index: 49)
Biometrical J.     Hybrid Journal   (Followers: 5, SJR: 0.784, h-index: 44)
Biometrics     Hybrid Journal   (Followers: 37, SJR: 1.906, h-index: 96)
Biopharmaceutics and Drug Disposition     Hybrid Journal   (Followers: 10, SJR: 0.715, h-index: 44)
Biopolymers     Hybrid Journal   (Followers: 18, SJR: 1.199, h-index: 104)
Biotechnology and Applied Biochemistry     Hybrid Journal   (Followers: 44, SJR: 0.415, h-index: 55)
Biotechnology and Bioengineering     Hybrid Journal   (Followers: 152, SJR: 1.633, h-index: 146)
Biotechnology J.     Hybrid Journal   (Followers: 14, SJR: 1.185, h-index: 51)
Biotechnology Progress     Hybrid Journal   (Followers: 39, SJR: 0.736, h-index: 101)
Biotropica     Hybrid Journal   (Followers: 20, SJR: 1.374, h-index: 71)
Bipolar Disorders     Hybrid Journal   (Followers: 9, SJR: 2.592, h-index: 100)
Birth     Hybrid Journal   (Followers: 38, SJR: 0.763, h-index: 64)
Birth Defects Research Part A : Clinical and Molecular Teratology     Hybrid Journal   (Followers: 2, SJR: 0.727, h-index: 77)
Birth Defects Research Part B: Developmental and Reproductive Toxicology     Hybrid Journal   (Followers: 7, SJR: 0.468, h-index: 47)
Birth Defects Research Part C : Embryo Today : Reviews     Hybrid Journal   (SJR: 1.513, h-index: 55)
BJOG : An Intl. J. of Obstetrics and Gynaecology     Partially Free   (Followers: 247, SJR: 2.083, h-index: 125)

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Journal Cover Advanced Engineering Materials
  [SJR: 0.81]   [H-I: 81]   [26 followers]  Follow
    
   Hybrid Journal Hybrid journal (It can contain Open Access articles)
   ISSN (Print) 1438-1656 - ISSN (Online) 1527-2648
   Published by John Wiley and Sons Homepage  [1589 journals]
  • Editorial
    • Authors: Sandra Kalveram; Jolke Perelaer
      PubDate: 2018-01-16T09:46:49.771677-05:
      DOI: 10.1002/adem.201701078
       
  • Masthead: Adv. Eng. Mater. 1∕2018
    • PubDate: 2018-01-16T09:46:49.32227-05:0
      DOI: 10.1002/adem.201870002
       
  • Front Cover: Advanced Engineering Materials 1∕2018
    • Abstract: The first fabrication of high-entropy alloy (HEA)- coated 3D nanolattice structure with the characteristic feature sizes spanning from 5 nm to 20 ìm is reported, demonstrating enhanced mechanical property. The design concept of combining HEA with five or more different metal elements and 3Dprinted hierarchical lattice structure would lead to new insights in developing structural metamaterials with tunable properties. Further information can be found in the article 1700625 by Yang Lu and co-workers.
      PubDate: 2018-01-16T09:46:46.397662-05:
      DOI: 10.1002/adem.201870001
       
  • Back Cover: Advanced Engineering Materials 1∕2018
    • Abstract: Utilizing the superior robustness in SiC, Hoang Phuong Phan and co-workers develop a fabrication process which applies photolithography directly on free-standing sub-100nm membranes to form a variety of MEMS structures. This technique eliminates the sticking and under-etch effects, and enables metallization on suspended SiC membranes for self-sensing applications. Further information can be found in the article 1700858.
      PubDate: 2018-01-16T09:46:39.646475-05:
      DOI: 10.1002/adem.201870003
       
  • Polysilazane-Type Coatings on Mo–Si–B Alloys: A Thermodynamic
           Assessment of the Phase Composition
    • Authors: Iryna Smokovych; Michael Scheffler
      Abstract: Thermodynamic analysis is conducted to identify the most probable phase composition of a polysilazane-type coating system on Mo–Mo3Si(A15)–Mo5SiB2(T2) alloy. The Free Gibbs Energy of chemical reactions between these constituents and resulting phases are calculated. Silicon nitrides, silicon oxynitrides, and molybdenum silicides have been found in the phase equilibrium between the gas phase and condensed species of the proposed coating system. Silicon oxynitride and silica as components in the coating system are potential candidates for Mo–Si–B alloy oxidation protection in air at high temperatures.This paper combines a theoretical/thermodynamic assessment of the phase formation between MoSiB and a polymer derived ceramic coating, in which a polysilazane is used for coating of Mo–Mo3Si(A15)–Mo5SiB2(T2) alloy. Based on the phase equilibrium of the model systems, the predicted phase composition of the coatings may act as a protecting passivation layer on the surface of Mo–Si–B alloys.
      PubDate: 2018-01-16T05:55:53.775529-05:
      DOI: 10.1002/adem.201700936
       
  • Latent Heat Thermal Energy Storage Systems with Solid–Liquid Phase
           Change Materials: A Review
    • Authors: Nan Zhang; Yanping Yuan, Xiaoling Cao, Yanxia Du, Zhaoli Zhang, Yewei Gui
      Abstract: This paper provides a review of the solid–liquid phase change materials (PCMs) for latent heat thermal energy storage (LHTES). The commonly used solid–liquid PCMs and their thermal properties are summarized here firstly. Two major drawbacks that seriously limit the application of PCMs in an LHTES system, that is, low thermal conductivity and liquid leakage, are discussed. Various methods for enhancing the thermal conductivity and heat transfer of solid–liquid PCMs are explained. Previous studies regarding form-stable composite PCMs and microencapsulated PCMs are also presented. Furthermore, applications of the solid–liquid PCMs used in LHTES and thermal management systems are introduced and analyzed. Finally, future outlooks and research topics are proposed.This paper provides a review of the solid–liquid phase change materials (PCMs) for latent heat thermal energy storage. The thermal properties and shortcomings of the PCMs are summed up firstly. Then, performance improvements of PCMs are discussed. And the applications used for thermal energy storage and thermal management are analyzed. Finally, the future research hotspots of PCMs are proposed.
      PubDate: 2018-01-15T05:18:58.90993-05:0
      DOI: 10.1002/adem.201700753
       
  • Porous Titanium Implants: A Review
    • Authors: Krzysztof Pałka; Rafał Pokrowiecki
      Abstract: Titanium and its alloys are commonly used in almost all disciplines of medicine because of their sufficient biocompatibility and meeting of mechanical requirements. However, dense metallic biomaterials represent only an interfacial connection with host tissue, may develop stress shielding which causes ingrowth of the fibrous tissue, and are prone to microbial adhesion and development of biomaterial associated infections. Therefore, development of a new, porous titanium biomaterial is proposed to improve an implant's interconnection with bone, provide better stabilization, and reduce the risk of the loss of the implant. In this review, recent findings in porous titanium biomaterials engineering are discussed, including the structural and strengthening aspects of titanium alloys. The porosity and design of porous structures, as well as the optimization process are also described. An extensive part of this section is dedicated to manufacturing processes. The next section of the review is devoted to osseointegration of porous implants and surface treatment processes, whose purpose are antibacterial activity or local drug delivery. Summarizing the article, some future predictions have been presented.Recent findings in the engineering of porous titanium are discussed in this work, including materials aspects. The porosity and design of porous structures, as well as the optimization process and manufacturing are also described. The next part of the review is devoted to osseointegration of porous implants and surface treatment processes, whose purpose are antibacterial activity or local drug delivery.
      PubDate: 2018-01-15T05:18:35.706614-05:
      DOI: 10.1002/adem.201700648
       
  • Heterogeneous Strain Distribution and Saturation of Geometrically
           Necessary Dislocations in a Ferritic–Pearlitic Steel during Lubricated
           Sliding
    • Authors: Mathias Linz; Manel Rodríguez Ripoll, Christoph Pauly, Johannes Bernardi, Andreas Steiger-Thirsfeld, Friedrich Franek, Frank Mücklich, Carsten Gachot
      Abstract: The microstructural evolution of ferritic–pearlitic steel is studied during unidirectional sliding under boundary lubrication using a ball-on-flat configuration. Dislocation activity as a function of distance to surface is determined using orientation gradients by electron backscatter diffraction in logarithmic intervals up to one million of sliding cycles. The orientation gradient results show the formation of geometrically necessary dislocations and low-angle grain boundaries, followed by a consolidation of those grain boundaries as nanocrystalline grains. The density of geometrically necessary dislocations and low-angle grain boundaries is observed to reach a steady state after around 100 000 cycles. Plastic strain is not homogeneously distributed within both material phases, that is, ferrite and pearlite. Most of the plastic deformation is carried by the ferritic phase. The heterogeneous strain distribution between the ferritic and the pearlitic phase observed in the electron backscatter diffraction measurements is attributed to stress incompatibilities at the grain boundaries. Dislocation pile-up at the ferritic–pearlitic interface is observed at high resolution using transmission electron microscopy and transmission Kikuchi diffraction.The microstructural evolution in sliding contacts is an important aspect in tribology. In this research study, the microstructural changes in a ferritic/pearlitic steel are analyzed with high resolution techniques such as EBSD in a boundary lubricated contact up to 106 cycles. The plastic strain is not homogeneously distributed between ferrite and pearlite. Ferrite carries most of plastic strains.
      PubDate: 2018-01-15T05:18:26.881085-05:
      DOI: 10.1002/adem.201700810
       
  • Oxidation Behavior between 700 and 1300 °C of Refractory TiZrNbHfTa
           High-Entropy Alloys Containing Aluminum
    • Authors: Chia-Hsiu Chang; Michael S. Titus, Jien-Wei Yeh
      Abstract: Refractory alloys without Cr, Al, and Si additions exhibit very poor high temperature oxidation resistance and thus significantly limit their applications. With an aim to improve the poor oxidation resistance of strong and ductile refractory TiZrNbHfTa high-entropy alloys (HEAs), this study investigates the effect of Al additions on the oxidation behavior and mechanisms for Al0-1TiZrNbHfTa HEAs. Higher Al content renders the alloy more resistant to oxidation. The AlTiZrNbHfTa alloy exhibits a mass gain twice of that of conventional Ni-based alloys at 1100 °C for 1 h, but much less than Nb refractory alloys because an Al-containing oxide on the surface layer provides a partial barrier against oxidation between 700 and 1100 °C. But, at 1300 °C the Al-containing alloys exhibit poor oxidation resistance because the less dense oxide layers provide oxygen with an effective diffusional channel and enable oxygen to penetrate the substrate more easily.This study investigates the effect of Al additions on the oxidation behavior and mechanisms for strong and ductile Al0-1TiZrNbHfTa HEAs. Higher Al content provides the alloy more resistance to oxidation and pesting. The authors speculate that a partial barrier against oxidation is established between 700 and 900 °C; however, at 1300 °C the Al-containing alloys still exhibit poor oxidation resistance.
      PubDate: 2018-01-15T05:18:11.691154-05:
      DOI: 10.1002/adem.201700948
       
  • Grain Size Depending Dwell-Fatigue Crack Growth in Inconel 718
    • Authors: Jonas Saarimäki; Mattias Lundberg, Johan J. Moverare
      Abstract: Inconel 718 is a commonly used superalloy for turbine discs in the gas turbine industry. Turbine discs are normally subjected to dwell-fatigue as a result of long constant load cycles. Dwell-times have been shown to give rise to increased crack propagation rates in superalloys at elevated temperatures. Dwell-time crack propagation behavior in Inconel 718 has been tested at 550 °C using Kb test samples with 2160 s dwell-times at maximum load and “pure fatigue” tests. The dwell-time effect has been studied for differently processed Inconel 718, that is, fine grained bar, grain enlarged bar, and cast material. This has been done in order to investigate the effect of grain size on crack propagation. Microstructure characterization is conducted using scanning electron microscopy techniques such as electron channeling contrast imaging and electron backscatter diffraction. Time dependent crack propagation rates are strongly affected by grain size. Propagation rates increase with decreasing grain size, whereas crack tip blunting increased with increasing grain size.Dwell-fatigue testing has been conducted on Inconel 718 with three different grain sizes, ≈20 μm, ≈200 μm, and>700 μm. Time dependent crack propagation rates are strongly affected by grain size. Propagation rates increase with decreasing grain size, whereas crack tip blunting increases with increasing grain size.
      PubDate: 2018-01-15T05:18:01.940575-05:
      DOI: 10.1002/adem.201700930
       
  • On the Mechanical Properties of Aluminum Matrix Syntactic Foams
    • Authors: Imre Norbert Orbulov; Attila Szlancsik
      Abstract: Metal matrix syntactic foams (MMSFs, often referred as composite metal foams (CMFs)) are lightweight materials with high specific strength. MMSFs are on the borderline between metal matrix composites and metal foams. On one hand MMSFs are composites, because they are filled by hollow particles and the particles may add strength to the material. On the other hand, they are foams, because the hollow particles ensure porosity to the material. Among metallic foams, MMSFs exhibit outstanding specific mechanical properties due to the hollow inclusions that are typically made from ceramics or high strength alloys, therefore they can be applied as structural materials. The goal of this paper is to summarize the available data on the mechanical properties of MMSFs with aluminum matrix in order to give a strong support to the design engineers. Since the foams are most frequently loaded in compression, the main part of this paper is organized around the available standard related to the compressive properties of porous materials and metallic foams. The quasi-static results are complemented by properties measured at higher strain rates. Besides this, some insight into the basic fatigue properties as well as into the toughness of MMSFs is also provided.The aim of the manuscript is to summarize the available literature data on the mechanical properties of metal matrix syntactic foams, also called composite metal foams. As the most important mechanical property of the foams is the compressive strength, the figure represents the data survey on this property, highlighting the limits, and relationships to the relative densities.
      PubDate: 2018-01-11T12:42:28.433001-05:
      DOI: 10.1002/adem.201700980
       
  • Transformation Pathway upon Heating of Ti–Fe Alloys Deformed by
           High-Pressure Torsion
    • Authors: Mario J. Kriegel; Askar Kilmametov, Martin Rudolph, Boris B. Straumal, Alena S. Gornakova, Hartmut Stöcker, Yulia Ivanisenko, Olga Fabrichnaya, Horst Hahn, David Rafaja
      Abstract: The current work presents the results of a study of the thermal stability of metastable ω-Ti(Fe) produced by a high-pressure torsion process and describes the phase transformations of ω-Ti(Fe) upon heating. The titanium alloys under study contain between 1 and 7 wt% of iron, the phase transitions are investigated using a combination of in situ high-temperature X-ray diffraction and differential scanning calorimetry. The high-temperature X-ray diffraction reveals the phase sequence ω  α'  α + β  β upon heating. The differential scanning calorimetry shows that the first phase transformation is exothermal and that the temperature of this phase transition is independent of the iron concentration within the composition range under study. Subsequent phase transitions are endothermal and the respective transition temperatures depend on the iron concentration. The differences between the phase stabilities conclude from the phase diagram and the phase stabilities observe experimentally are explained by the partial coherence of the α/α′-Ti and β-Ti grains.This article presents a study of the thermal stability of metastable ω-Ti(Fe) produced by a high-pressure torsion process. The high-temperature X-ray diffraction reveals the phase sequence ω  α'  α + β  β upon heating. The differences between the phase stabilities concluded from the phase diagram and the phase stabilities observed experimentally are explained by the partial coherence of the α/α′-Ti and β-Ti grains.
      PubDate: 2018-01-05T07:57:55.426204-05:
      DOI: 10.1002/adem.201700933
       
  • Solid State Porous Metal Production: A Review of the Capabilities,
           Characteristics, and Challenges
    • Authors: Mark A. Atwater; Laura N. Guevara, Kris A. Darling, Mark A. Tschopp
      Abstract: Porous metals have been under development for nearly a century, but commercial adoption remains limited. This development has followed two primary routes: liquid state or solid state processing. Liquid state foaming introduces porosity to a liquid or semi-solid metal, and solid state foaming introduces porosity to a metal, which is fully solid. Either method may create pores by internal gas pressure or introducing metal around a template directly control porosity. Process optimization and commercial output has been primarily related to liquid state methods, as solid state processing is often more complex, diverse, and with lower throughput. Solid state methods, however, are often more versatile and offer greater control of pore characteristics. Ongoing advancements in solid state foaming have allowed for a wide array of metals and alloys to be made porous and the three-dimensional structure to be precisely tailored. In general, solid state processing remains limited to niche applications, often with modest dimensions (cm scale). “Traditional” solid state processes are being further refined and extended, and continuing developments to reduce cost, increase output, and control pore characteristics are likely to produce important advancements in coming years. The extensive variability of pore quantity and morphology makes solid state processes suitable, and often preferable, for an assortment of functional and structural applications, with electrodes and biomedical devices being among the most popular in current research. Various techniques for introducing porosity, the way these methods are applied, important considerations, typical outcomes, and current applications are reviewed.Porous metals have been studied for decades, but production challenges have limited widespread adoption. These are being addressed in an increasing number of publications, especially on solid state methods. Advancements, capabilities, and applications of these methods and materials are reviewed.
      PubDate: 2018-01-04T07:11:01.426069-05:
      DOI: 10.1002/adem.201700766
       
  • Impact Toughness of Ultrafine-Grained Commercially Pure Titanium for
           Medical Application
    • Authors: Alexander Vadimovich Polyakov; Irina Petrovna Semenova, Elena Vladimirovna Bobruk, Seung Mi Baek, Hyoung Seop Kim, Ruslan Zufarovich Valiev
      Abstract: This study aims at achieving the best combination of strength, ductility, and impact toughness in ultrafine-grained (UFG) Ti Grade 4 produced by equal-channel angular pressing via Conform scheme (ECAP-C) with subsequent cold drawing. UFG structures with various parameters (e.g., size and shape of grains, dislocation density, conditions of boundaries) are formed by varying the treatment procedures (deformation temperature and speed at drawing, annealing temperature). The tensile and impact toughness tests were performed on samples with a V-shaped notch and different structures of commercially pure Ti Grade 4 in the coarse-grained and UFG states. The results demonstrated that grain refinement, higher dislocation density, and their elongated shape were obtained as a result of drawing at 200 °С, which led to a decrease in both the uniform elongation at tension and the impact toughness of Ti Grade 4. Short-term annealing at 400–450 °C could improve the impact toughness of UFG Ti with a non-significant decrease in strength. This short-term annealing contributes to the dislocation density decrease without considerable grain growth as a result of the recovery and redistribution of dislocations. The dependence of impact toughness on the strain hardening ability of UFG Ti was discussed.This study is focused on possibility of achieving the high impact toughness in UFG Ti rods processed by ECAP-Conform with subsequent drawing. It is demonstrated that the annealing at 425–450 °C for 30 min can improve the impact toughness from 85 to 130 kJ m–2 of UFG Ti with a non-significant decrease in tensile strength.
      PubDate: 2018-01-04T07:10:39.521437-05:
      DOI: 10.1002/adem.201700863
       
  • The Hydride Precipitation Mechanisms in the Hydrogenated Weld Zone of
           Ti–0.3Mo–0.8Ni Alloy Argon-Arc Welded Joints
    • Authors: Quan-Ming Liu; Zhao-Hui Zhang, Shi-Feng Liu, Hai-Ying Yang
      Abstract: A review of the microstructural evolution and phase transformation in the hydrogenated weld zone of Ti–0.3Mo–0.8Ni alloy argon-arc welded joints has been considered. The role of crystallographic, microstructural, and precipitation mechanisms on the defect-free properties of the hydrogenated weld zone has been analyzed, and hydride phase formations have been revealed by the influence of hydrogen on the microstructural characteristics of the weld zone. The results show face-centered cubic (FCC) δ and face-centered tetragonal (FCT) γ hydride phase formations are found in the hydrogenated 0.21 wt% H weld zone. Large lamellar, slender plate δ and long needle γ hydrides can only precipitate from the alpha lamellae, and not from the transformed beta phase due to the high hydrogen solubility found in the beta phase. Formation of the δ and γ hydrides are the result of αH phase separation reaction: αH  α (H lean region) + δ (H rich region) and αH  γ (H rich region), respectively. The precipitation mechanisms and characteristics of the δ and γ hydrides formed in alpha phase are discussed in detail. Dislocation multiplication around the hydrides is promoted effectively by hydrogen addition, the fact that the quantity of dislocations around the δ hydride increased obviously compared to γ hydride indicated the αH  δ phase transformation result in a greater volume expansion rate.Based on the strong affinity of titanium alloys and hydrogen, the hydrogenated titanium alloys welded joints with a series of hydrogen contents as a high incidence area of hydrogen embrittlement have been used for the study of hydrides precipitation types, characteristics, and mechanisms in details.
      PubDate: 2018-01-04T07:05:53.144324-05:
      DOI: 10.1002/adem.201700679
       
  • Solid-State Supercapacitor Fabricated in a Single Woven Textile Layer for
           E-Textiles Applications
    • Authors: Sheng Yong; John Owen, Stephen Beeby
      Abstract: This paper presents for the first time a solid-state supercapacitor fabricated in just a single woven cotton textile layer. The controlled spray coating process enables the depth of the activated carbon electrodes to be precisely controlled from both sides of the textile. This leaves an uncoated region within the cotton textile layer that acts as the separator and also minimizes the effect of the added functional materials on the feel of the textile. The cotton electrode is then vacuum impregnated with the gel electrolyte to ensure good coverage of the electrode by the electrolyte. After drying, the single textile layer supercapacitor has been fully characterized and demonstrates good capacitance and excellent electrochemical cycling stability even after mechanically straining the textile.In this work, a single layer solid state cotton textile supercapacitor is fabricated by a combination of and inexpensive carbon solution, spray coating, and vacuum impregnation process. The dried device has been characterized and demonstrates good capacitance and excellent electrochemical cycling stability even after mechanically straining the textile.
      PubDate: 2018-01-04T07:05:35.795526-05:
      DOI: 10.1002/adem.201700860
       
  • Recent Advances on 3D Printing Technique for Thermal-Related Applications
    • Authors: Nam Nguyen; Jin Gyu Park, Songlin Zhang, Richard Liang
      Abstract: Advances in ink formulation and printing techniques make producing material systems with new and versatile characteristics and functionalities possible. Additive manufacturing or 3D printing enables fabricating complex structures at a faster production rate using different types of materials for various applications. Recently, 3D printing methods are being studied for thermal-related applications. In this paper, the authors review recent progress of materials and printing techniques for thermal application devices using composite materials.The authors summarize recent progress of materials and printing techniques for thermal-related application devices such as heat sink, heater, or thermal interface materials. Current challenges and opportunity related to the printing thermal-related devices are also discussed in the paper.
      PubDate: 2018-01-03T11:06:16.821007-05:
      DOI: 10.1002/adem.201700876
       
  • Transparency in Structural Glass Systems Via Mechanical, Adhesive, and
           Laminated Connections - Existing Research and Developments
    • Authors: Chiara Bedon; Manuel Santarsiero
      Abstract: The consistent architectural transparency demand in buildings is highly promoting the structural use of glass, in combination or to replace load-bearing components made of traditional constructional materials. Despite its huge application in facades, roofs, envelopes, frame components, however, glass still represents a rather innovative and not well-known material, requiring specific design conceptsm and further extended studies, toward the fulfillme nt of safe design requirements. A key role in glass systems and assemblies involving multiple components is given to connections. Major issues in their design, consequently, arise from restraining single glazing elements, as well as from ensuring their mechanical interaction with other constructional systems, as a part of full 3D buildings, including several materials, and various loading/boundary conditions. In this paper, an overview of typical connection types in use for glass systems is presented, with special consideration for mechanical, adhesive, and laminated adhesive connections, giving evidence of their typical applications, evolution, current design issues. Existing research and major projects are also discussed, both at the material/component level as well as at the assembly level.Structural glass is largely used in buildings, in combination or to replace load-bearing components made of traditional constructional materials. However, glass still represents a rather innovative and not well-known material, requiring specific design concepts and studies, especially in terms of connections. The paper presents an overview of typical connections in use for glazing systems, with special consideration for mechanical, adhesive and laminated adhesive solutions, giving evidence of typical applications, evolution, design issues.
      PubDate: 2018-01-03T06:48:17.962236-05:
      DOI: 10.1002/adem.201700815
       
  • Bioinspired Nacre-Like Ceramic with Nickel Inclusions Fabricated by
           Electroless Plating and Spark Plasma Sintering
    • Authors: Zhe Xu; Jiacheng Huang, Cheng Zhang, Soheil Daryadel, Ali Behroozfar, Brandon McWilliams, Benjamin Boesl, Arvind Agarwal, Majid Minary-Jolandan
      Abstract: Hybrid composites of layered brittle-ductile constituents assembled in a brick-and-mortar architecture are promising for applications requiring high strength and toughness. Mostly, polymer mortars have been considered as the ductile layer in brick-and-mortar composites. However, low stiffness of polymers does not efficiently transfer the shear between hard ceramic bricks. Theoretical models point to metals as a more efficient mortar layer. However, infiltration of metals into ceramic scaffold is non-trivial, given the low wetting between metals and ceramics. The authors report on an alternative approach to fabricate brick-and-mortar ceramic-metal composites by using electroless plating of nickel (Ni) on alumina micro-platelets, in which Ni-coated micro-platelets are subsequently aligned by a magnetic field, taking advantage of ferromagnetic properties of Ni. The assembled Ni-coated ceramic scaffold is then sintered using spark plasma sintering (SPS) to locally create Ni mortar layers between ceramic platelets, as well as to sinter the ceramic micro-platelets. The authors report on materials and mechanical properties of the fabricated composite. The results show that this approach is promising toward development of bioinspired ceramic-metal composites.Bioinspired ceramic-metal composite is fabricated by electroless-plating of Nickel (metal) on ceramic (aluminum oxide) microplates. The metal-coated platelets are subsequently aligned by magnetic field and sintered by spark plasma sintering process. The composite shows desirable crack-deflection properties.
      PubDate: 2018-01-02T04:20:34.141423-05:
      DOI: 10.1002/adem.201700782
       
  • Novel Antibacterial and Bioactive Silicate Glass Nanoparticles for
           Biomedical Applications
    • Authors: Ana Catarina Vale; Ana Luísa Carvalho, Ana Margarida Barbosa, Egídio Torrado, João F. Mano, Natália M. Alves
      Abstract: In this work, the authors propose a new quick sol–gel procedure for bioglass nanoparticles production containing 10% mol of silver (AgBGs). These new AgBGs are characterized by Zeta potential analysis, scanning electron microscopy with X-ray microanalysis (SEM/EDS), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and microbiological tests to confirm their bioactive and antibacterial properties. SEM shows that the average particle size is less than 200 nm and EDS confirms the successful incorporation of Ag2O in the bioglass matrix. XRD confirms the amorphous nature of the AgBGs and, after SBF immersion, reveals their bioactive behavior with the presence of crystalline phase of calcium silicate and phosphorus oxide, which are also detected by FTIR analysis. FTIR also confirms the formation of typical siloxane bonds resulting from the condensation of silicate glass. Lastly, it is found that the developed AgBGs has an antibacterial effect against two different types of bacteria, thus demonstrating their ability to reduce the bacterial infection within 16 h.Bioglass nanoparticles with silver content are of interest, since they provide the combination of important properties. As the image shows, this work presents the production and characterization of new silver doped nanoparticles, confirming their bioactive and antibacterial properties, which are crucial for several biomedical applications.
      PubDate: 2017-12-27T02:25:30.534797-05:
      DOI: 10.1002/adem.201700855
       
  • The Occurrence of Ideal Plastic State in CP Titanium Processed by Twist
           Extrusion
    • Authors: Aleksey Reshetov; Roman Kulagin, Alexander Korshunov, Yan Beygelzimer
      Abstract: This paper deals with the analysis of strength and plastic characteristics of commercially pure (CP) titanium as a function of equivalent plastic strain accumulated during Twist Extrusion (TE) process. It is shown experimentally that multipass TE leads to the saturation of the following characteristics of the material: yield stress, reduction in area, elongation to failure, and uniform elongation. This fact indicates the occurrence of an ideal plastic state in the processed material. The threshold value of accumulated plastic strain for ideal plastic behavior of CP titanium during TE is defined. The strain state and mechanical properties of CP titanium billets processed by TE are studied. An explanation for the hardening on the axis of a billet during TE is offered. The analysis of deformation modes on the billet axis during TE and High Pressure Torsion is carried out. It is shown that the differences in strain state on the axis are caused by the difference in symmetry of these processes.It is shown experimentally that multipass TE leads to the saturation of mechanical properties in the billet. This fact indicates the occurrence of an ideal plastic state. An explanation for the hardening central zone of the billet during TE is offered.
      PubDate: 2017-12-21T05:06:20.647846-05:
      DOI: 10.1002/adem.201700899
       
  • Additive Manufacturing of Titanium Alloys by Electron Beam Melting: A
           Review
    • Authors: Lai-Chang Zhang; Yujing Liu, Shujun Li, Yulin Hao
      Abstract: Electron beam melting (EBM), as one of metal additive manufacturing technologies, is considered to be an innovative industrial production technology. Based on the layer-wise manufacturing technique, as-produced parts can be fabricated on a powder bed using the 3D computational design method. Because the melting process takes place in a vacuum environment, EBM technology can produce parts with higher densities compared to selective laser melting (SLM), particularly when titanium alloy is used. The ability to produce higher quality parts using EBM technology is making EBM more competitive. After briefly introducing the EBM process and the processing factors involved, this paper reviews recent progress in the processing, microstructure, and properties of titanium alloys and their composites manufactured by EBM. The paper describes significant positive progress in EBM of all types of titanium in terms of solid bulk and porous structures including Ti–6Al–4V and Ti–24Nb–4Zr–8Sn, with a focus on manufacturing using EBM and the resultant unique microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM-produced titanium alloys.Electron beam melting (EBM), a metal additive manufacturing technology, has the ability to produce high quality metal parts. This paper reviews recent progress in all types of titanium alloys in terms of solid and porous structures, with a focus on the microstructure and service properties (mechanical properties, fatigue behaviors, and corrosion resistance properties) of EBM-produced titanium alloys.
      PubDate: 2017-12-19T04:26:43.181635-05:
      DOI: 10.1002/adem.201700842
       
  • Finite Element Analysis as a Method to Study Molluscan Shell Mechanics
    • Authors: Robert Lemanis; Igor Zlotnikov
      Abstract: The clade Mollusca is a highly diverse and disparate group of terrestrial and aquatic invertebrates, the taxon containing over 100 000 known species including some of the most intelligent invertebrate animals. Their shells are exemplar systems in the study of biomechanics, biomineralization, and biomimetics. Research into understanding the superior biomechanical properties of the shell and how these properties relate to the animals ecology have required a diverse range of methods at multiple length scales; one particularly powerful method is finite element analysis. Finite element analysis is a robust engineering method that has a long-standing history in biomechanical research. This review summarizes the application of finite element analysis in the study of both the mechanical properties of different molluscan shell ultrastructures as well as macro-scale modeling of the shell. From the calculation of elastic constants to the origins of the strength of nacre and the relationship between shell folding and ecology, this article provides a window into how finite element analysis can further our understanding of mechanics and functional morphology.Decades of research have gone into the study of the molluscan shell using a variety of methods. Here, the authors review how one particular method, finite element analysis, has been used to further our understanding of the mechanical properties and functional morphology of the shell at both the ultrastructural and macro-structural levels.
      PubDate: 2017-12-18T07:42:13.035821-05:
      DOI: 10.1002/adem.201700939
       
  • Formation of Cu Nanodots on Diamond Surface to Improve Heat Transfer in
           Cu/D Composites
    • Authors: Thomas Guillemet; Jean-Marc Heintz, Bruno Mortaigne, Yongfeng Lu, Jean-François Silvain
      Abstract: Diamond-dispersed copper matrix (Cu/D) composite materials with different interfacial configurations are fabricated through powder metallurgy and their thermal performances are evaluated. An innovative solution to chemically bond copper (Cu) to diamond (D) has been investigated and compared to the traditional Cu/D bonding process involving carbide-forming additives such as boron (B) or chromium (Cr). The proposed solution consists of coating diamond reinforcements with Cu particles through a gas–solid nucleation and growth process. The Cu particle-coating acts as a chemical bonding agent at the Cu–D interface during hot pressing, leading to cohesive and thermally conductive Cu/D composites with no carbide-forming additives. Investigation of the microstructure of the Cu/D materials through scanning electron microscopy, transmission electron microscopy, and atomic force microscopy analyses is coupled with thermal performance evaluations through thermal diffusivity, dilatometry, and thermal cycling. Cu/D composites fabricated with 40 vol% of Cu-coated diamonds exhibit a thermal conductivity of 475 W m−1 K−1 and a thermal expansion coefficient of 12 × 10−6 °C−1. These promising thermal performances are superior to that of B-carbide-bonded Cu/D composites and similar to that of Cr-carbide-bonded Cu/D composites fabricated in this study. Moreover, the Cu/D composites fabricated with Cu-coated diamonds exhibit higher thermal cycling resistance than carbide-bonded materials, which are affected by the brittleness of the carbide interphase upon repeated heating and cooling cycles. The as-developed materials can be applicable as heat spreaders for thermal management of power electronic packages. The copper-carbon chemical bonding solution proposed in this article may also be found interesting to other areas of electronic packaging, such as brazing solders, direct bonded copper substrates, and polymer coatings.Diamond-dispersed copper matrix (Cu/D) composite materials with different interfacial configurations are fabricated through powder metallurgy and their thermal performances are evaluated. An innovative solution to chemically bond copper to diamond has been investigated that consists of coating diamond reinforcements with Cu particles through a gas–solid nucleation and growth process.
      PubDate: 2017-12-18T03:50:10.544513-05:
      DOI: 10.1002/adem.201700894
       
  • Robust Free-Standing Nano-Thin SiC Membranes Enable Direct
           Photolithography for MEMS Sensing Applications
    • Authors: Hoang-Phuong Phan; Tuan-Khoa Nguyen, Toan Dinh, Alan Iacopi, Leonie Hold, Muhammad J. A. Shiddiky, Dzung Viet Dao, Nam-Trung Nguyen
      Abstract: This work presents fabrication of micro structures on sub–100 nm SiC membranes with a large aspect ratio up to 1:3200. Unlike conventional processes, this approach starts with Si wet etching to form suspended SiC membranes, followed by micro-machined processes to pattern free-standing microstructures such as cantilevers and micro bridges. This technique eliminates the sticking or the under-etching effects on free-standing structures, enhancing mechanical performance which is favorable for MEMS applications. In addition, post-Si-etching photography also enables the formation of metal electrodes on free standing SiC membranes to develop electrically-measurable devices. To proof this concept, the authors demonstrate a SiC pressure sensor by applying lithography and plasma etching on released ultrathin SiC films. The sensors exhibit excellent linear response to the applied pressure, as well as good repeatability. The proposed method opens a pathway for the development of self-sensing free-standing SiC sensors.Utilizing the superior robustness in SiC, this work develops a fabrication process which applies photolithography directly on free-standing sub-100 nm membranes to form a variety of MEMS structures. This technique eliminates the sticking and under-etch effects and enables metallization on suspended SiC membranes for self-sensing applications.
      PubDate: 2017-12-15T04:31:49.305827-05:
      DOI: 10.1002/adem.201700858
       
  • Combined Microwave and Laser Heating for Glazing of 8Y–ZrO2 and
           8Y–ZrO2/ZrSiO4–Composites
    • Authors: Christian Richter; Sebastian Lehmann, Jens Böckler, Monika Willert-Porada, Andreas Rosin
      PubDate: 2017-12-14T09:15:44.920659-05:
      DOI: 10.1002/adem.201700912
       
  • Modulation of Agglomeration of Vertical Porous Silicon Nanowires and the
           Effect on Gas-Sensing Response
    • Authors: Yuxiang Qin; Yunqing Jiang, Liming Zhao
      Abstract: Porous silicon nanowires (PSiNWs) array is a promising material for development of integrated gas sensors operating at room temperature. This work reports the fabrication of PSiNWs assembly with different structural features and its effect on gas-sensing performance. Bundling and well separating PSiNWs arrays are fabricated by MACE method, respectively, based on the effective modulation of surface wettability of the initial Si substrate. The HF pretreatment creates a hydrophobic surface favorable for deposition of irregular Ag nanoflakes and then for the formation of bundling PSiNWs array. In contrast, the PSiNWs with well lateral separation are formed based on the predeposited uniform Ag nanoparticles on a hydrophilic Si surface. The PSiNWs array featured by tip-clusters is proved to be highly effective in achieving highly sensitive and rapid response to NO2 gas at room temperature. Satisfying dynamic characteristic and selectivity are meanwhile observed for the bundling array. The formation of the bundling or separating of PSiNWs is discussed in terms of the force balance of individual nanowire, which is further correlated with non-uniform distribution of Ag nanoclusters caused by H-termination. Meanwhile, high sensing performance of bundling nanowires is analyzed based on the structural promotion of the unique configuration of tip-cluster to sensing response.Bundling and well separating porous silicon nanowires (PSiNWs) arrays are, respectively, fabricated based on the effective modulation of surface wettability of initial Si substrate. The PSiNWs array featured by tip-clusters is demonstrated as a highly effective configuration for gas-sensing application; highly sensitive and rapid response to NO2 gas is achieved at room temperature.
      PubDate: 2017-12-14T09:06:26.834812-05:
      DOI: 10.1002/adem.201700893
       
  • Preparations, Characteristics and Applications of the Functional Liquid
           Metal Materials
    • Authors: Qian Wang; Yang Yu, Jing Liu
      Abstract: As new generation functional materials, the recently emerging low-melting liquid metals have displayed many unconventional properties superior to traditional materials. Various methods, such as alloying, oxidizing, adding metals, or non-metallic materials and so on, have been developed to prepare desirable functional materials based on the gallium or more other metals. These methods could not only change the form of the materials, but also endow the original liquid metals with rather diversified performances, which have further expanded the application range of the low-melting liquid metals to meet various needs. This article aims to review and summarize on the fabrication methods, characteristics, and applications of the functional liquid metal materials. Furthermore, the future outlook in this field, including challenges, routes, and related efforts, has also been illustrated and interpreted.The low melting point liquid metals have recently been disclosed with many outstanding unconventional properties superior to traditional materials. This article comprehensively reviews and summarizes the most typical fabrication methods, unique characteristics, and important applications of such functional materials. The future outlook in this field, including challenges, developing routes, and related efforts has also been illustrated and interpreted.
      PubDate: 2017-12-13T06:03:22.20866-05:0
      DOI: 10.1002/adem.201700781
       
  • Composition Dependence on the Evolution of Nanoeutectic in CoCrFeNiNbx
           (0.45 ≤ x ≤ 0.65) High Entropy Alloys
    • Authors: Barnasree Chanda; Jayanta Das
      Abstract: The effect of Nb addition in arc-melted CoCrFeNiNbx (0.45 ≤ x ≤ 0.65) high entropy alloys (HEAs) on the phase evolution, stability, refinement of the microstructure, and mechanical properties are investigated. Minor fluctuation of Nb modifies the microstructure from hypoeutectic (x = 0.45) to eutectic (x = 0.5) and hypereutectic (x = 0.55) containing 134–200 nm thin nano-lamellar FCC γ-Ni and HCP Fe2Nb-type Laves phases. The nano-eutectic CoCrFeNiNb0.5 HEA shows high yield strength (2060 ± 5 MPa) and strain hardening up to 2200 ± 10 MPa with 17.0 ± 0.5% compressive plasticity. Transmission electron microscopic studies of partially deformed specimen has been revealed that the activity of dislocations is present in the eutectic FCC/Laves lamellae and at their interface. The stability of the phases in CoCrFeNiNbx and other eutectic HEAs as reported in the literature, has been assessed by estimating mixing entropy (ΔSmix), mixing enthalpy (ΔHmix), atomic size differences (δ), valence electron concentration, Pauling electronegativity (ΔχP), and Allen electronegativity (ΔχA) to predict the evolution and coexistence of eutectic phases.The microstructure of CoCrFeNiNbx (0.45 ≤ x ≤ 0.65) high entropy alloys contain proeutectic dendrites along with nanolamellar γ-Ni and Laves phases, which show high yield strength of 2060 MPa and large plasticity of 17% due to the movement of dislocations. The stability of the phases has been assessed using thermodynamic parameter, atomic size parameter, valance electron concentration, and electronegativity parameters.
      PubDate: 2017-12-13T05:36:18.715984-05:
      DOI: 10.1002/adem.201700908
       
  • Utilizing Low-Cost Eggshell Particles to Enhance the Mechanical Response
           of Mg–2.5Zn Magnesium Alloy Matrix
    • Authors: Gururaj Parande; Vyasaraj Manakari, Sripathi Dev Sharma Kopparthy, Manoj Gupta
      Abstract: The search for lightweight high-performance materials is growing exponentially primarily due to ever-increasing stricter environmental regulations and stringent service conditions. To cater to these requirements, the use of low-cost reinforcements has been explored in the Mg matrix to develop Economically Conscious Magnesium (ECo–Mg) composites. In this study, eggshell particles (3, 5, and 7 wt%) reinforced Mg–Zn composites are synthesized using blend-press-sinter powder metallurgy technique. The results reveal that the addition of eggshell particles enhances microhardness, thermal stability, damping, and yield strength with an inappreciable change in the density. In particular, Mg2.5Zn7ES composite do not ignite till ≈750 °C. The overall combination of properties exhibited by Mg–Zn–ES composites exceeds many of currently used commercial alloys in the transportation sector. An attempt is made, in this study, to interrelate microstructure and properties and to study the viability of compression and ignition properties with a comparison to commercially used Mg alloys.This work investigates the influence of low-cost reinforcement (eggshell) on the microstructural, mechanical and damping enhancement of Mg–Zn alloy using low-cost synthesis methodology (powder metallurgy technique). Mg–Zn–eggshell composites display superior property enhancement better than most commercially available Mg alloys and are a potential replacement material in several engineering and biomedical applications.
      PubDate: 2017-12-13T04:56:38.58965-05:0
      DOI: 10.1002/adem.201700919
       
  • Additive Manufacturing of Advanced Multi-Component Alloys: Bulk Metallic
           Glasses and High Entropy Alloys
    • Authors: Xiaopeng Li
      Abstract: Bulk metallic glasses (BMGs) and high entropy alloys (HEAs) are both important multi-component alloys with novel microstructures and unique properties, which make them promising for applications in many industries. However, certain hindrances have been identified in the fabrication of BMGs and HEAs by conventional techniques due to the intrinsic requirements of BMGs and HEAs. With the advent of metal additive manufacturing, new opportunities have been perceived to fabricate geometrically complex BMGs and HEAs with tailorable microstructure theoretically at any site within the specimen, which are not achievable using conventional fabrication techniques. After providing some background and introducing the conventional fabrication techniques for BMGs and HEAs, this review will focus on the current status, development, and challenges in metal additive manufacturing of BMGs and HEAs including different additive manufacturing techniques being used, microstructure design and evolution, as well as properties of the fabricated BMGs and HEAs. A future outlook of metal additive manufacturing of BMGs and HEAs will also be provided at the end.Additive manufacturing has become a promising alternative for the fabrication of advanced multi-component alloys such as bulk metallic glasses (BMGs) and high entropy alloys (HEAs). Due to the intrinsic layer-wise fabrication process of additive manufacturing, more complex and large scale BMGs and HEAs components with controllable local microstructure and properties can be achieved.
      PubDate: 2017-12-12T08:28:01.13502-05:0
      DOI: 10.1002/adem.201700874
       
  • Super-High Strength Mg–7.5Al–0.8Zn Alloy Prepared by Rapidly
           Solidified Powder Metallurgy and Low Temperature Extrusion
    • Authors: Jian Zhu; Junxiu Liu, Yi Wang, Kuang Lu, Jinbin Chen, Zikui Liu, Xidong Hui
      Abstract: In this work, Mg–7.5Al–0.8Zn alloy with super-high tensile strength are fabricated by rapidly solidified powder metallurgy (RS/PM) and low temperature extrusion technology. By reducing extrusion temperature from 340 to 170 °C, the α-Mg grains are significantly refined and numerous nanoscale β-Mg17Al12 particles are obtained. The RS/PM alloy extruded at 170 °C possesses the lowest grain size of ≈550 nm. The nanoscale β-phase particles stimulate the nucleation of dynamically recrystallized (DRXed) grains and restrain the growth of DRXed grains. The RS/PM alloy extruded at 170 °C exhibits mechanical properties with a tensile yield strength of 448 MPa, an ultimate tensile strength of 480 Mpa, and a microhardness of 137 HV. These excellent mechanical properties result from low temperature extrusion are mainly attributed to the ultra-fine DRXed grains and the high-density dislocations and subgrains.The effects of extrusion temperatures are investigated on the microstructures and mechanical properties of RS/PM Mg–7.5Al–0.8Zn alloys. The mechanical properties of RS/PM alloys are remarkably improved by reducing extrusion temperatures from 340 to 170 °C.
      PubDate: 2017-12-12T08:26:40.746323-05:
      DOI: 10.1002/adem.201700712
       
  • Controlled Friction Behaviors of Porous Copper/Graphite Storing Ionic
           Liquid through Electrical Stimulation
    • Authors: Guoliang Zhang; Guoxin Xie, Jie Wang, Lina Si, Dan Guo, Shizhu Wen, Fan Yang
      Abstract: Porous copper/graphite composites storing stimuli-responsive lubricant can be used to fabricate a new kind of electrical contact friction materials. However, the synergetic lubricating effect of solid and liquid lubricants incorporated into the copper matrix is rarely discussed. In this work, neat copper and its composites storing ionic liquids (ILs) have been successfully prepared via a template-free strategy. The effect of frictional, electrical, and electro-frictional coupling stimulation on the tribological behavior of the copper filled with graphite has been investigated using ball-on-disk friction tests. Results show that a high voltage may accelerate the release of the ILs stored in the composite to the friction interface, thereby resulting in a low coefficient of friction (COF) (ca. 0.14) at the voltage of 0.5 V, which is superior to those of the pure copper without applying voltage. The COF is more stable in copper/graphite composite storing ILs (SI) than in copper-SI. Therefore, the graphite efficiently protects the surface of the sample from wear and electrochemical corrosion.The ionic liquids (ILs) stored in the pores of the copper matrix respond to the frictional, electrical, and electro-frictional coupling stimulation has been investigated using ball-on-disk friction tests under external electric fields. A proper voltage may accelerate the release of the ILs to the friction interface, thereby resulting in a low coefficient of friction.
      PubDate: 2017-12-11T07:26:26.768903-05:
      DOI: 10.1002/adem.201700866
       
  • Spin Valve Effect of 2D-Materials Based Magnetic Junctions
    • Authors: Muhammad Zahir Iqbal; Salma Siddique, Ghulam Hussain
      Abstract: The magnetotransport properties of spin valve structure are highly influenced by the type of intervening layer inserted between the ferromagnetic electrodes. In this scenario, spin filtering effect at the interfaces plays a crucial role in determining the magnetoresistance (MR) of such magnetic structures, which can be enhanced by using a suitable intervening layer. Here, the authors investigate the spin filtering effect of the two-dimensional layers such as hexagonal boron nitride (hBN), graphene (Gr), and Gr-hBN hybrid system for modifying the magnetotransport characteristics of the vertical spin valve architectures (Ni/hBN/Ni, Ni/Gr/Ni, and Ni/Gr-hBN/Ni). Compared to graphene, hBN incorporated magnetic junction reveals higher MR and spin polarizations (P) suggesting better spin filtering at the interfaces. The MR for hBN incorporated junction is calculated to be ≈0.83%, while that of graphene junction it is estimated to be ≈0.16%. Similar contrast is observed in the ‘P’ of ferromagnets (FMs) for the two junctions, that is, ≈6.4% for hBN based magnetic junction and ≈2.8% for graphene device. However, for Gr-hBN device, the signal not only get inverts, but it also suggests efficient spin filtering mechanism at the FM interfaces. Their results can be useful to comprehend the origin of spin filtering and the choice of non-magnetic spacer for magnetotransport characteristics.The authors investigate spin filtering mechanism by incorporating 2D materials in spin valve devices. Comparing to graphene, hBN device reveals pronounced spintronic features suggesting better spin filtering at the interfaces. Furthermore, graphene and hBN incorporated magnetic junctions reveal positive MR, while that for Gr-hBN heterostructure the signal not only becomes negative, but also facilitates efficient spin filtering at the interfaces.
      PubDate: 2017-12-11T07:25:58.015757-05:
      DOI: 10.1002/adem.201700692
       
  • Enhanced Mechanical Properties of Multilayered Cu with Modulated Grain
           Size Distribution
    • Authors: Bo Zheng; Xixun Shen, Huisheng Jiao, Qunjie Xu, Danhong Cheng
      Abstract: A bulk multilayered copper with nano-sized grains (NG) as hard layer and ultrafine grains (UFG) as soft layer with the thickness ratio of about 10:1 is synthesized by electrodeposition. Microstructural studies by scanning electron microscope (SEM) and transmission electron microscope (TEM) reveal the alternating growth of well-defined layers with either nano-grains or ultrafine-grains. Tensile tests reveal that the layered nanostructured Cu exhibits an enhanced ductility of near 17.5% and high ultimate tensile strength of about 700 MPa. The multilayered Cu exhibits a higher ductility without obvious loss of strength compared to the monolithic nano-grained Cu. The enhanced ductility is primarily attributed to two effects including the increased strain hardening ability and the effective adjustment to the local stress concentration brought by the periodic existence of the UFG layer in the NG matrix.A bulk multilayered Cu with the alternating growth of nano-grained layer and ultrafine grained layer with the thickness ratio of about 10:1 is synthesized by electrodeposition technique. The multilayered Cu exhibits a better combination of high ductility and high strength in comparison with the corresponding monolithic nano-grained and ultrafine-grianed Cu.
      PubDate: 2017-12-08T08:15:47.382134-05:
      DOI: 10.1002/adem.201700849
       
  • Fabrication of Metallic Fibers with High Melting Point and Poor
           Workability by Unidirectional Solidification
    • Authors: Yuui Yokota; Takayuki Nihei, Kunihiro Tanaka, Koichi Sakairi, Valery Chani, Yuji Ohashi, Shunsuke Kurosawa, Kei Kamada, Akira Yoshikawa
      Abstract: Innovative method acceptable for production of Iridium (Ir) and Ruthenium (Ru) metal fibers with high melting point and poor workability is developed using an alloy-micro-pulling-down (A-μ-PD) method and ceramic crucibles with sufficient mechanical and thermal shock resistance. As-grown (as-solidified) Ir and Ru fibers are approximately 1 mm in diameter and their lengths exceed 15 and 0.3 m, respectively. Both Ir and Ru fibers are composed of number of elongated grains oriented along a growth direction, which is attributable to the unidirectional solidification. The flexibility and oxidation resistance of the Ir fiber grown by the A-μ-PD method is considerably improved as compared to a commercial Ir wire made by wire-drawing process.Innovative method acceptable for production of Iridium and Ruthenium metal fibers with high melting point and poor workability are developed using an alloy-micro-pulling-down (A-μ-PD) method and ceramic crucibles with sufficient mechanical and thermal shock resistance. The Iridium and Ruthenium fibers are composed of number of elongated grains oriented along the growth direction, which is attributable to the unidirectional solidification.
      PubDate: 2017-12-07T08:08:41.149519-05:
      DOI: 10.1002/adem.201700506
       
  • Effect of Dynamically Recrystallized Grains on Rare Earth Texture in
           Magnesium Alloy Extruded at High Temperature
    • Authors: Rongguang Li; Guangyan Fu, Zeren Xu, Yong Su, Yongsheng Hao
      Abstract: This work investigates texture evolution in an Mg–3Gd–0.2Al alloy during extrusion and after annealing at 500 °C. It shows that the dynamically recrystallized (DRX) grains formed in grain boundaries and twins have different influence on texture evolution. After extrusion, the DRX grains that nucleated at grain boundaries have texture distributing from ED to ED, while these in twins do from ED to ED. After further annealing process, the ED component is strengthened and become the dominating texture component, which results in a strong rare earth (RE) texture. Thus, the RE texture is mainly attributed to the preferential nucleation at grain boundaries during extrusion and the privileged growth of the grains with ED orientation during annealing.A trace of {10–11}–{10–12} double-twin is identified. Orientation of double-twin is close to ED, and ones of DRX grains range from ED to ED. Thus, DRX grains within twins have orientations close to that of twins.
      PubDate: 2017-12-07T08:08:29.621419-05:
      DOI: 10.1002/adem.201700818
       
  • Effects of Initial δ Phase on Creep Behaviors and Fracture
           Characteristics of a Nickel-Based Superalloy
    • Authors: Y. C. Lin; Liang-Xing Yin, Shun-Cun Luo, Dao-Guang He, Xiao-Bin Peng
      Abstract: Uniaxial creep tensile experiments are performed to study the influences of initial δ phase (Ni3Nb) on the creep features and fracture behaviors of a nickel-based superalloy. Experimental results show that the creep features and fracture behaviors of the researched superalloy are closely relevant to the volume fraction of initial δ phase. The minimum creep rate increases with the increased volume fraction of initial δ phase. The appropriate volume fraction of initial δ phase can improve the creep resistance and plasticity. So, the rupture time and the elongation to fracture initially increase, when the volume fraction of initial δ phase is relatively low, and then decrease with the increase of volume fraction of initial δ phase. Additionally, with the increased initial δ phase, the failure mode changes from a typical intergranular fracture to the mixed fracture pattern of ductile intergranular and cleavage fracture.Effects of initial δ phase (Ni3Nb) on uniaxial creep behavior and fracture characteristics of a nickel-based superalloy are investigated. The appropriate initial δ phase fraction can improve the creep resistance and plasticity. The increased initial δ phase changes the failure mode from a typical intergranular fracture to the ductile intergranular/cleavage mixed fracture.
      PubDate: 2017-12-06T08:45:39.29225-05:0
      DOI: 10.1002/adem.201700820
       
  • Recent Progress on Piezotronic and Piezo-Phototronic Effects in III-Group
           Nitride Devices and Applications
    • Authors: Chunhua Du; Weiguo Hu, Zhong Lin Wang
      Abstract: Wurtzite-structured III-group nitrides, like GaN, InN, AlN, and their alloys, present both piezoelectric and semiconducting properties under straining owing to the polarization of ions in a crystal with non-central symmetry. The piezoelectric polarization charges are created at the interface when a strain is applied. As a result, a piezoelectric potential (piezopotential) is produced, which is used as a “gate” to tune/control the charge transport behavior across a metal/semiconductor interface or a p-n junction. This is called as piezotronic effect. A series of piezotronic devices and applications have been developed, such as piezotronic nanogenerators (NGs), piezotronic transistors, piezotronic logic devices, piezotronic electromechanical memories, piezotronic enhanced biochemical, and gas sensors and so on. With the flourished development of piezotronic effect, the piezo-phototronic effect, as the three-way coupling of piezoelectric polarization, semiconductor properties, and optical excitation, utilizes the piezopotential to modulate the energy band profile and control the carrier generation, transportation, separation, and/or recombination for improving performances of optoelectronic devices. This paper intends to provide an overview of the rapid progress in the emerging fields of piezotronics and piezo-phototronics, covering from the fundamental principles to devices and applications. This study will provide important insight into the potential applications of GaN based electronic/optoelectronic devices in sensing, active flexible/stretchable electronics/optoelectronics, energy harvesting, human-machine interfacing, biomedical diagnosis/therapy, and prosthetics.Wurtzite-structured III-group nitrides have been widely used for developing the revolutionary multifunctional electronics/optoelectronics based on heterojunction, quantum well and superlattice structures. Due to non-central symmetry of crystal lattice, piezopotential is generated by applying mechanical force/stress to tune/control the carriers' generation, transportation, and/or recombination, which is the core of the piezotronic and piezo-phototronic effects.
      PubDate: 2017-12-06T06:11:17.594249-05:
      DOI: 10.1002/adem.201700760
       
  • Toward High Strength and High Electrical Conductivity in Super-Aligned
           Carbon Nanotubes Reinforced Copper
    • Authors: Lunqiao Xiong; Kangwei Liu, Jing Shuai, Zecheng Hou, Lin Zhu, Wenzhen Li
      Abstract: The miniaturization of electronic products is drawing higher demand in the strength and conductivity of conductors. This work demonstrates the possibility of substantially increasing the dislocation density in copper to enhance the strength of super-aligned carbon nanotubes (SACNTs) reinforced copper matrix composites (SACNT/Cu) without compromising the electrical conductivity. High strain is introduced into pure copper and SACNT/Cu by accumulative roll-bonding (ARB) process up to 16 cycles at ambient temperature. SACNTs with initial laminated distribution turn out to be dispersed uniformly with maintained directional arrangement inside the copper matrix after ARB, which can then effectively block the motion of dislocations. Therefore, large number of dislocations propagated by large strains can be accumulated without subdivision. The accumulated dislocations will result into strain hardening, which is the major strengthening mechanism in SACNT/Cu after ARB. Furthermore, the contribution of dislocations to resistivity increase is little, thus maintaining high electrical conductivity. As a result, a high tensile strength (505 MPa) combined with a high electrical conductivity (90% IACS) is achieved in large-sized composite sheet.The strength of super-aligned carbon nanotubes (SACNTs) reinforced copper matrix composite is substantially enhanced without compromising the conductivity by increasing the dislocation density in copper. The dispersed distribution of SACNTs can effectively block dislocation motion, thus delaying grain refinement during accumulative roll-bonding process. High strength and high electrical conductivity copper matrix composite can, therefore, be mass-produced.
      PubDate: 2017-12-05T09:41:10.364439-05:
      DOI: 10.1002/adem.201700805
       
  • Illuminating Origins of Impact Energy Dissipation in Mechanical
           Metamaterials
    • Authors: Peter Vuyk; Shichao Cui, Ryan L. Harne
      Abstract: Elastomeric mechanical metamaterials have revealed striking ability to attenuate shock loads at the macroscopic level. Reports suggest that this capability is associated with the reversible elastic buckling of internal beam constituents observed in quasistatic characterizations. Yet, the presence of buckling members induces non-affine response at the microscale, so that clear understanding of the exact energy dissipation mechanisms remains clouded. In this report, the authors examine a mechanical metamaterial that exhibits both micro- and macroscopic deformations under impact loads and devise an experimental method to visualize the resulting energy dissipation mechanisms. By illuminating the dynamic distribution of strain in the metamaterial, the authors uncover a rational way to program the macroscopic deformation and enhance impact mitigation properties. The results emphasize that mechanical metamaterials clearly integrate materials science and structural engineering, encouraging future interdisciplinary studies to capitalize on the opportunities.Elastomeric mechanical metamaterials that include internal buckling beam members are effective to dissipate impact energy. The authors uncover the origins of the energy dissipation mechanisms by a digital image correlation technique that illuminates the strain distributions exemplified in the figure. With this knowledge, the authors explore and verify new ways to program mechanical metamaterials for enhanced impact mitigation properties.
      PubDate: 2017-12-05T09:26:27.103824-05:
      DOI: 10.1002/adem.201700828
       
  • Microstructure and Mechanical Properties of Ti2AlNb-Based Alloys
           Synthesized by Spark Plasma Sintering from Pre-Alloyed and Ball-Milled
           Powder
    • Authors: Mengchen Li; Qi Cai, Yongchang Liu, Zongqing Ma, Zumin Wang
      Abstract: Ti2AlNb-based alloys are synthesized by spark plasma sintering from pre-alloyed and ball-milled Ti–22Al–25Nb powder, and the structure of the alloys is regulated by aging at 800 °C for 0.5, 1, 2, and 3 h. Comparison of phase composition, microstructure, and mechanical properties are made in this study. Aging in the B2 + O phase region refers to the reversible transformation of B2  O. Complete B2 + O Widmanstätten structure is obtained in the aged alloys synthesized from pre-alloyed powder, and the ones from milled powder contain acicular O and B2 + O Widmanstätten structure. Ball milling eliminates the B2 + O colonies, facilitates the continuous transformation of O  B2, and induces acicular O in the alloys; however, the hardness of these alloys is decreased in contrast with that of the ones synthesized from pre-alloyed powder. Owing to the precipitation strengthening based on a large amount of fine O-phase precipitates, the 3 h aged alloy from pre-alloyed powder exhibits comprehensive mechanical properties with Vickers hardness of 448 ± 9 HV, ultimate tensile strength of 730 MPa, and elongation of 0.43%.Ti2AlNb alloys are synthesized by spark plasma sintering and aged at 800 °C. Besides Widmanstätten B2 + O, the typical microstructure is B2 + O colonies and acicular O for alloys from pre-alloyed and ball-milled powder, respectively. Due to precipitation strengthening of O phase, favorable mechanical properties are obtained with hardness of 448 ± 9 HV, ultimate tensile strength of 730 MPa, and elongation of 0.43%.
      PubDate: 2017-12-04T04:27:10.822908-05:
      DOI: 10.1002/adem.201700659
       
  • On the Wetting States of Low Melting Point Metal Galinstan® on
           Silicon Microstructured Surfaces
    • Authors: Ethan Davis; Sidy Ndao
      Abstract: The primary goal of this article is to measure the wetting characteristics of a low melting point metal to determine the efficacy of this type of material for possible use in thermal energy storage applications. Galinstan®, a commercially available alloy consisting of Gallium, Indium, and Tin is subjected to contact angle measurements on various silicon surfaces at varying temperatures. Due to the oxidation characteristics of Galinstan, all experiments are conducted in an inert nitrogen environment (
      PubDate: 2017-12-04T04:15:37.033303-05:
      DOI: 10.1002/adem.201700829
       
  • Toward Functional 3D Architectured Platform: Advanced Approach to Anchor
           Functional Metal Oxide onto 3D Printed Scaffold
    • Authors: Junghyun Choi; Patrick Joo Hyun Kim, Jihoon Seo, Jiseok Kwon, Sangkyu Lee, Taeseup Song
      Abstract: The authors first report the three-dimensional (3D) structured CeO2–PLA scaffold using a 3D printing methodology. The scaffold is prepared by decorating functional metal-oxide nanoparticles onto the 3D-printed polylactic acid (PLA) platform via an electrostatic interaction and is applied to the applications for photochemical degradation. As-designed CeO2–PLA scaffold shows high photocatalytic degradation performance toward methyl orange under a light irradation. Furthermore, the CeO2–PLA scaffold shows reasonable degradation performance even after it is washed and reevaluated; this result demonstrates the benefit of 3D-printed CeO2–PLA scaffold that it can be recycled several times without losing the catalysts.The authors fabricate the 3D printed scaffold with metal oxide decoration. Positive charged metal oxide nanoparticle electrostatically interacts with negative charged 3D printed polylactic acid scaffold. Metal oxide decorated scaffold is demonstrated as a photocatalyst. It shows reasonable photocatalytic performance and possibility of reusable. Our facile methodology is able to extend to the application fields of 3D printing.
      PubDate: 2017-12-04T04:05:52.040574-05:
      DOI: 10.1002/adem.201700901
       
  • Fabrication and Properties of Micro- and Nanoscale Metallic Glassy Wires:
           A Review
    • Authors: Jun Yi
      Abstract: A large number of metallic glasses (MGs) with high mechanical and functional performance that cannot be achieved by traditional metals in various alloy systems have been developed. At the same time, people realized that micro- and nanoscale wires can improve properties and extend functionality of bulk materials. Therefore, intensive effort has been made to fabricate micro- and nanoscale MG wires, and study their mechanical and physical behavior to achieve high performance. This article reviews fabrication, properties and applications of the wires, and presents technical and theoretical challenges, which must be tackled to achieve high-performance MG wire devices and understand physical mechanisms of mechanical and functional behaviors of the wires.This paper critically reviews fabrication, mechanical, and functional behavior of micro- and nanoscale metallic glassy wire wires and their physical mechanisms, and highlights the state of the art of the wires. In addition, this paper delineates technical and theoretical challenges, which will be tackled to achieve high-performance metallic glassy wire devices and further understanding of the physical mechanisms.
      PubDate: 2017-12-01T08:05:46.203661-05:
      DOI: 10.1002/adem.201700875
       
  • Initiated Chemical Vapor Deposition: A Versatile Tool for Various Device
           Applications
    • Authors: Seung Jung Yu; Kwanyong Pak, Moo Jin Kwak, Munkyu Joo, Bong Jun Kim, Myung Seok Oh, Jieung Baek, Hongkeun Park, Goro Choi, Do Heung Kim, Junhwan Choi, Yunho Choi, Jihye Shin, Heeyeon Moon, Eunjung Lee, Sung Gap Im
      Abstract: Advances in device technology have been accompanied by the development of new types of materials and device fabrication methods. Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for surface modification using functional thin film. The building of polymeric thin films from vapor phase monomers is highly desirable for the surface modification of thermally sensitive substrates. The precise control of thin film thicknesses can be achieved using iCVD, creating a conformal coating on nano-, and micro-structured substrates such as membranes and microfluidics. iCVD allows for the deposition of polymer thin films of high chemical functionality, and thus, substrate surfaces can be functionalized directly from the iCVD polymer film or can selectively gain functionality through chemical reactions between functional groups on the substrate and other reactive molecules. These beneficial aspects of iCVD can spur breakthroughs in device fabrication based on the deposition of robust and functional polymer thin films. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.Considering device design, initiated chemical vapor deposition (iCVD) inspires innovation as a platform technology that extends the application range of a material or device. iCVD serves as a versatile tool for direct building of polymeric thin films on substrates from vapor phase monomers. This review describes significant implications of and recent progress made in iCVD-based technologies in three fields: electronic devices, surface engineering, and biomedical applications.
      PubDate: 2017-11-30T05:56:54.537649-05:
      DOI: 10.1002/adem.201700622
       
  • Drop-on-Demand Inkjet Printing of Thermally Tunable Liquid Crystal
           Microlenses
    • Authors: Ellis Parry; Serena Bolis, Steve J. Elston, Alfonso A. Castrejón-Pita, Stephen M. Morris
      Abstract: In this letter, the authors demonstrate Drop-on-Demand printing of variable focus, polarization-independent, liquid crystal (LC) microlenses. By carefully selecting the surface treatment applied to a glass substrate, the authors are able to deposit droplets with a well-defined curvature and contact angle, which result in micron-sized lenses with focal lengths on the order of 300–900 µm. Observations with an optical polarizing microscope confirm the homeotopic alignment of the LC director in the droplets, which is in accordance with the polarization independent focal length. Results show that microlenses of different focal lengths can be fabricated by depositing successive droplets onto the same location on the substrate, which can then be used to build up programmable and arbitrary arrays of microlenses of various lens sizes and focal lengths. Finally, the authors utilize the thermal dependency of the order parameter of the LC to demonstrate facile tuning of the focal length. This technique has the potential to offer a low-cost solution to the production of variable focus, arbitrary, microlens arrays.Tuneable microlens arrays are fabricated via the drop-on-demand inkjet printing of a nematic liquid crystal onto a polymer coated substrate. The programmable and arbitrary microlens arrays produced exhibit excellent polarization independent focussing properties with high numerical apertures.
      PubDate: 2017-11-29T07:45:29.485099-05:
      DOI: 10.1002/adem.201700774
       
  • Texture and Electromagnetic Coupling Properties
    • Authors: Luis Edmundo Fuentes-Cobas; María Cristina Grijalva-Castillo, Luis Fuentes-Montero, José Andrés Matutes-Aquino, Juan Méndez-Nonell
      Abstract: The estimation of physical properties in textured polycrystals is reviewed. “Principal” properties, which relate actions and responses within the same subsystem (electric, elastic, …), as well as “coupling” properties (e.g., piezomagnetism), linking actions, and responses associated with various subsystems (magneto-elastic, thermo-electric, …) are analyzed. Tensor ranks from 1 to 4, with polar and axial characteristics are considered. Virtual-time inversion (the case of magnetoelectricity) is taken into account. Matrix and surface representations are considered. Significant differences in the effect of texture on properties arise from the diversity of properties tensors ranks and polar/axial natures. To predict the effective values of coupling properties, precautions required for application of the Voigt, Reuss, and Hill approximations are pointed out. At all stages of the proposed methodology, a symmetrized spherical harmonics treatment of the orientation distribution functions, the inverse pole figures and (single- and polycrystals) physical properties is applied. For the case of magnetostriction, a functional program for estimating polycrystal performance is included as Supporting Information. The input data are the single-crystal property coefficients and the polycrystal inverse pole figure parameters. The coincidence of predicted magnetostriction coefficients with experimentally measured values is satisfactory. Recently established considerations regarding the characterization of coupling properties in complex materials are divulged.Crystallographic texture plays an important role in materials' performance. In this article, the authors review the diversity of texture properties relationships found in functional materials. Several coupling interactions are analyzed. The figure shows the case of galfenol magnetostriction as a function of axial texture.
      PubDate: 2017-11-29T07:11:02.798681-05:
      DOI: 10.1002/adem.201700827
       
  • Creep Behavior of High-Nb TiAl Alloy at 800–900 °C by
           Directional Solidification
    • Authors: Qi Wang; Ruirun Chen, Yaohua Yang, Jingjie Guo, Yanqing Su, Hongsheng Ding, Hengzhi Fu
      Abstract: Cold crucible directional solidification Ti44Al6Nb1.0Cr alloy is crept at 800–900 °C. Experimental results show that creep lifetime significantly decreases with the increasing creep temperature. When creeping at 900 °C under 130 MPa, the TQ twinning is activated in lamellar structures. The TQ twinning shows a strong dependency on temperature during creep under low creep-stress and it can overcome α2 lamellae and transfer into adjacent γ lamellae. The hardening by mechanical twinning and the softening by α2 lamellar dissolution take place at different zones in lamellar structures and the strain incompatibility between hardening zone and softening zone promotes the microcracks to form in lamellar structures. The deformation characteristic of hard and soft lamellae is studied. Moreover, recrystallization γ phase formed in lamellar structures near colony boundary during creep at 900 °C accelerates the creep failure.Ti-44Al-6Nb-1.0Cr alloy is crept at 800–900 ºC. TQ twinning is activated in lamellar structures during creep at 900 ºC/130 MPa and it overcomes α2 lamella and transfers into adjacent γ lamella. Hardening by mechanical twinning and softening by α2 lamellar dissolution tack place at different zones.
      PubDate: 2017-11-28T08:21:03.977748-05:
      DOI: 10.1002/adem.201700734
       
  • Effect of Sc and Zr on Microstructure and Mechanical Properties of As-Cast
           Al–Li–Cu Alloys
    • Authors: Yang Wang; Zheng Li, Tianfu Yu, Aboubakr Medjahed, Ruizhi Wu, Legan Hou, Jinghuai Zhang, Xinlin Li, Milin Zhang
      Abstract: Effect of Sc and Zr addition on microstructure and mechanical properties of as-cast Al–Li–Cu alloys are investigated. The results show that, a significant grain refinement can be caused by Sc and Zr. The coarse dendritic microstructure is transformed into equiaxed grains after adding Sc and Zr. The refinement can be attributed to the primary particles, Al3(Sc,Zr), of which the orientation is close to that of α-Al matrix. The primary particles prevent the unsuitable diffusion and act as heterogeneous nucleation sites for α-Al in the process of solidification. The model for the multi-layer structure evolution of primary particle is established. Moreover, the mechanical properties of as-cast Al–Li–Cu–Sc–Zr alloy are affected markedly because of the addition of Sc and Zr. The solid solution strengthening and Hall–Petch strengthening are primary strengthening mechanisms, YS = ΔσHPS + Δσsss + 104 (MPa).The coarse dendritic microstructure is transformed into equiaxed grains after adding Sc and Zr. The refinement can be attributed to the primary particles, Al3(Sc,Zr). The model for the multi-layer structure evolution of primary particle is established. The solid solution strengthening and Hall–Petch strengthening are primary strengthening mechanisms, YS = ΔσHPS+Δσsss+104(MPa).
      PubDate: 2017-11-28T05:11:17.308112-05:
      DOI: 10.1002/adem.201700898
       
  • Inorganic Thin Film Deposition and Application on Organic Polymer
           Substrates
    • Authors: Jitesh Hora; Colin Hall, Drew Evans, Eric Charrault
      Abstract: This review details the emerging area of inorganic thin film coatings on polymer substrates, from examples of applications through to the fabrication processes and the underlying growth mechanism(s). Of particular focus is the use of physical vapor deposition to deposit thin metal and/or metal oxide films onto polymeric materials. This primary focus highlights an area of research, that is, gaining in popularity, as researchers attempt to provide insight into the adaption of a well-established manufacturing process to be compatible with the ever expanding range of polymer substrates. The motivation for doing so comes from the evolution of existing industry (i.e., the semi-conductor sector) to fabricate new devices (i.e., flexible electronics). In addition, the research challenges faced in achieving evaporated and sputtered thin film coatings on polymeric substrates, such as mechanical and thermal considerations will be discussed.Regardless of chemistry, molecular weight and substrate type (thick solid polymer bulk, foil or thin layer deposited onto another substrate), the inherent properties of polymers present challenges throughout the whole PVD process. Overcoming these challenges and enhancing the resultant thin film performance is critical for the advancement of new technology, such as flexible electronics.
      PubDate: 2017-11-28T05:11:03.398898-05:
      DOI: 10.1002/adem.201700868
       
  • Enhanced Thermal Conductivity of 5A Molecular Sieve with BNs Segregated
           Structures
    • Authors: Nan Sun; Quan-Ping Zhang, Hao-Ran Sun, Wen-Bin Yang, Yuan-Lin Zhou, Jiang-Feng Song, De-Li Luo
      Abstract: 5A molecular sieves have been widely used as adsorbents in cryogenic distillation for hydrogen isotope separation in fusion reactor engineering, but its low thermal conductivity is detrimental to the process stability. Improving the thermal conductivity of 5A molecular sieves is one of the most important goals for high-performance devices. Here, firm segregated structures with boron nitride sheets (BNs) are constructed around 5A molecular sieve particles. SEM results show 30 µm BNs tend to form the better networks in comparison with that of 0.12 µm BNs at 40 wt% loadings. It is further verified that BNs with the larger size promote the thermal conductivity. Meanwhile, the thermal conductivity increases with the increasing amounts of BNs. XRD and specific surface area results indicate that the sintering and the addition of BNs exert negligible effects on the structure of 5A molecular sieve. These results indirectly show 5A molecular sieve with BNs segregated structures is very likely to be used for the application of hydrogen isotopic separation. Besides, this work provides new insight into the construction of segregated structure in inorganic porous materials.Boron nitride sheets (BNs) are assembled on the surface of 5A molecular sieves via powder mixing. Firm segregated networks are successfully constructed by further compression and sintering for the mixed powders. This work provides a new insight into the fabrication of segregated structures in inorganic porous materials.
      PubDate: 2017-11-28T05:10:32.209911-05:
      DOI: 10.1002/adem.201700745
       
  • Optimization Techniques for Improving the Performance of Silicone-Based
           Dielectric Elastomers
    • Authors: Anne Ladegaard Skov; Liyun Yu
      Abstract: Dielectric elastomers are possible candidates for realizing products that are in high demand by society, such as soft robotics and prosthetics, tactile displays, and smart wearables. Diverse and advanced products based on dielectric elastomers are available; however, no elastomer has proven ideal for all types of products. Silicone elastomers, though, are the most promising type of elastomer when viewed from a reliability perspective, since in normal conditions they do not undergo any chemical degradation or mechanical ageing/relaxation. Within this review, different pathways for improving the electro-mechanical performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are investigated and discussed, with special emphasis placed on the promise each method holds. The compositing and blending of elastomers are shown to be simple, versatile methods that can solve a number of optimization issues. More complicated methods, involving chemical modification of the silicone backbone as well as controlling the network structure for improved mechanical properties, are shown to solve yet more issues. From the analysis, it is obvious that there is not a single optimization technique that will lead to the universal optimization of dielectric elastomer films, though each method may lead to elastomers with certain features, and thus certain potentials.Different pathways for improving the performance of dielectric elastomers are highlighted. Various optimization methods for improved energy transduction are discussed, with special emphasis placed on the promise each method holds. It is shown that there is not one single optimization technique that will lead to the universal optimization, though each method may lead to elastomers with certain features and potentials.
      PubDate: 2017-11-27T09:55:50.215442-05:
      DOI: 10.1002/adem.201700762
       
  • Corrugation Reinforced Composites: A Method for Filling Holes in
           Material-Property Space
    • Authors: Mark Fraser; Hatem S. Zurob, Peidong Wu
      Abstract: Material-property space is filled with holes representing desirable combinations of properties, such as high strength and high necking strain. One way to fill those holes is to use architectured materials. In this work, Finite Element Modeling (FEM) simulations are performed to evaluate composites with a corrugated reinforcement architecture across a range of volume fractions and corrugation heights for a model copper-steel system. The corrugated reinforcement geometry shows large improvements in necking strain, which increases with corrugation height, without sacrificing strength, and fills a desirable region in material-property space. Additionally, it is found that the necking strain of a matrix material can be increased by adding a less ductile reinforcing material provided it has a highly corrugated geometry. The improvement in necking strain seen in these composites is attributed to a boost in work hardening that results from an evolving reinforcement alignment as the corrugation unbends.In this work, Finite Element Modeling simulations demonstrated that corrugation reinforced composites with different geometries and volume fractions can access the hole in material-property space characterized by high strength and high necking strain. These composites improve on the necking strain of straight reinforced composites by taking advantage of a boost in work hardening that results from the unbending corrugations.
      PubDate: 2017-11-27T09:50:45.984875-05:
      DOI: 10.1002/adem.201700834
       
  • Tailoring Microstructure and Properties of Fine Grained Magnesium Alloys
           by Severe Plastic Deformation
    • Authors: Alexei Vinogradov; Vladimir N. Serebryany, Sergey V. Dobatkin
      Abstract: Modern wrought magnesium alloys have poor formability at room temperature, which impedes the wider uptake of these alloys by the industry. Over the last decades, research activities in the area of magnesium alloy development have grown enormously and have produced a pallet of exciting findings, which the authors summarize in this concise review focused on the effect of the microstructure, primarily of grain size, on room temperature ductility of wrought Mg-based alloys. Well-established paths and modern strategies to control over the grain size distribution are discussed. It is demonstrated that the use of severe plastic deformation techniques for ultimate grain refinement in magnesium alloys opens new windows for improving their mechanical properties profile by managing both strength and ductility in a wide range. However, it is shown that grain size alone cannot be regarded as a key parameter controlling the mechanical behavior of Mg alloys. The effect of texture is of paramount importance for the overall mechanical response of Mg alloys and this may supersede the influence of grain size.The severe plastic deformation techniques possess great flexibility in tailoring microstructures for desired combination of mechanical properties in structural materials. Routes to obtain an excellent balance of high strength and ductility in wrought magnesium alloys through a combination of grain refinement and texture control in the course of severe plastic deformation are discussed.
      PubDate: 2017-11-27T02:06:17.909176-05:
      DOI: 10.1002/adem.201700785
       
  • Flexible Triboelectric Nanogenerator Based on High Surface Area TiO2
           Nanotube Arrays
    • Authors: Raheleh Mohammadpour
      Abstract: Triboelectric nanogenerators (TENGs) can harvest mechanical energy through coupling triboelectric effect and electrostatic induction. Typically, TENGs consist of organic materials, however on account of the potentially wide range of applications of TENGs as the self-powered portable/wearable electronics, biomedical devices, and sensors; semiconductor metal oxide materials can be promising candidates to be incorporating in TENG structure. Here, flexible TENG based on self-organized TiO2 nanotube arrays (TNTAs) is fabricated via anodization method. The introduced flexible large area nanotubular electrode is employed as the moving electrode in contact with Kapton film in vertical contact separation mode of TENG. The fabricated TENG can deliver output voltage of 40 V with the current density of 1 μA cm−2. To evaluate the role of nanostructured interface, its performance has been compared to the thin film flat compact TiO2 electrode. The results of extracted charge measurements under short circuit condition indicate that larger triboelectric charge density formed in TNTA-based electrode (about 110 nC per cycle of press and release) is in comparison to 15 nC in flat TiO2 electrode. Due to the extensive range of applications of TiO2, the introduced structure can potentially be applicable in various types of self-powered systems such as photo-detectors and environmental gas and bio-sensors.Large scale flexible tribolectric nanogenerator (TENG) based on TiO2 nanotube arrays (TNTAs) can deliver output voltage of 40 V with the current density of 1 µA cm–2.
      PubDate: 2017-11-27T02:06:08.225484-05:
      DOI: 10.1002/adem.201700767
       
  • Polyethylene Glycol–CaCl2 Coordination Compounds as a Novel Form-Stable
           Phase Change Material with Excellent Thermophysical Properties
    • Authors: Qinrong Sun; Haiquan Zhang, Yanping Yuan, Xiaoling Cao, Liangliang Sun
      Abstract: Polyethylene glycols (PEGs) have been extensively studied as phase change materials (PCMs). To overcome the problem of liquid leakage, the authors firstly report a novel form-stable phase change material (FSPCM) using coordination compound. The structure, morphology, thermal property, and thermal stability of the self-prepared samples are determined. The obtained results confirm the existence of coordination bonds between PEG and Ca2+ species, and no liquid leakage is observed for the synthesized PEG–CaCl2 composites at temperatures as high as 120 °C. The PEG8000–CaCl2 (1:2) FSPCM exhibits a relatively large latent heat of 147.7 J g−1, corresponding to 87.8% of that of pure PEG. From the dynamical viewpoint, the activation energy of crystallization process is increased by only 5.2% for the PEG8000–CaCl2 composite due to the formation of coordination bonds; however, the activation energy is reduced by 18.3% during melting process. After adding 3 wt% conductive carbon black, the heat storage performance of the PEG phase change material can be optimized. The PEG-CaCl2 composite would be a promising material for thermal energy storage applications and can be used in various engineering fields.Part of the PEG polymer is converted into a three-dimensional framework by using coordination chemical bonds between PEG and Ca. This method can be one-step preparation of form-stable phase change material (PEGX-CaCl2).
      PubDate: 2017-11-23T09:11:38.194905-05:
      DOI: 10.1002/adem.201700643
       
  • Intelligent Sensing System Based on Hybrid Nanogenerator by Harvesting
           Multiple Clean Energy
    • Authors: Yuhang Xie; Hulin Zhang, Guang Yao, Saeed Ahmed Khan, Min Gao, Yuanjie Su, Weiqing Yang, Yuan Lin
      Abstract: The inexhaustible mechanical kinetic energy can be extracted from wind and flowing water. Besides, flowing water also possesses electrostatic energy owing to the triboelectric charges caused by contacting with surrounding media, such as air. Here, a rotating hybridized triboelectric nanogenerator (TENG) has been established, by comprising of a water-TENG (W-TENG), a disk-TENG (D-TENG), and an electromagnetic generator (EMG), which has been explored for simultaneously harvesting energies from flowing water and wind. The W-TENG is fabricated by wheel blades, polyvinylidene fluoride (PVDF), superhydrophobic polytetrafluoroethylene (PTFE), and aluminum to harvest the electrostatic energy. Moreover, the flowing water and wind impact on the wheel blades also causes the rotation motion of D-TENG and EMG, resulting in being converted into electricity. At the rotation speed of 200 rpm, the short circuit current of D-TENG and EMG can reach 0.4 μA and 7 mA, respectively. The open circuit voltage of W-TENG can be up to 10 V at a flowing water rate of 60 ml s−1. Besides, the hybridized NG is demonstrated to harvest water and wind energy and to act as a power source to charge a lithium battery or capacitor, which can drive LEDs, PH monitoring system, and wireless temperature and humidity sensing system. All these results show the potentials of the hybridized NG for harvesting multiple types of energies from the environment and constructing different self-powered systems.In this work, the authors demonstrate a new hybrid nanogenerator, which have been developed for simultaneously harvesting mechanical energies from flowing water and wind. The hybrid device can be employed to fabricate a wireless self-powered system for temperature and humidity sensing. This work promotes the development of renewable energy and presents a promising application for self-powered remote sensing.
      PubDate: 2017-11-23T09:11:30.807325-05:
      DOI: 10.1002/adem.201700886
       
  • A Review on Piezoelectric, Magnetostrictive, and Magnetoelectric Materials
           and Device Technologies for Energy Harvesting Applications
    • Authors: Fumio Narita; Marina Fox
      Abstract: In the coming era of the internet of things (IoT), wireless sensor networks that monitor, detect, and gather data will play a crucial role in advancements in public safety, human healthcare, industrial automation, and energy management. Batteries are currently the power source of choice for operating wireless network devices due to their ease of installation; however, they require periodic replacement due to capacity limitations. Within the scope of the IoT, battery maintenance of the trillion sensor nodes that may be implemented will be practically infeasible from environmental, resource, and labor cost perspectives. In considering individual self-powered sensor nodes, the idea of harvesting energy from ambient vibrations, heat, and electromagnetic waves has recently triggered noticeable research interest in the academic community. This paper gives an overview of energy harvesting materials and systems. Three main categories are presented: piezoelectric ceramics/polymers, magnetostrictive alloys, and magnetoelectric (ME) multiferroic composites. State-of-the-art harvesting materials and structures are presented with a focus on characterization, fabrication, modeling and simulation, and durability and reliability. Some perspectives and challenges for the future development of energy harvesting materials are also highlighted.Recent progress in piezoelectric ceramics/polymers, magnetostrictive alloys, and magnetoelectric (ME) multiferroic composites for energy harvesting applications is systematically summarized. A survey of the challenges in characterization, fabrication, modeling and simulation, and durability and reliability is presented.
      PubDate: 2017-11-21T08:56:01.381003-05:
      DOI: 10.1002/adem.201700743
       
  • Optimization of Strength-Electrical Conductivity Properties in Al–2Fe
           Alloy by Severe Plastic Deformation and Heat Treatment
    • Authors: Andrey E Medvedev; Maxim Y Murashkin, Nariman A Enikeev, Ruslan Z Valiev, Peter D Hodgson, Rimma Lapovok
      Abstract: High-pressure torsion at room temperature followed by two processing routes, either 1) annealing at 200 °C for 8 h or 2) elevated temperature (200 °C) high-pressure torsion, are employed to obtain simultaneous increase in mechanical strength and electrical conductivity of Al–2 wt%Fe. The comparative study of microstructure, particle distribution, mechanical properties, and electrical conductivity for both processing routes gives the optimal combination of high mechanical strength and high electrical conductivity in Al–2Fe alloy. It is shown that while the mechanical strength is approximately the same for both processing routes (>320 MPa), high-pressure torsion at elevated temperature results in higher conductivity (≥52% IACS) due to reduction of Fe solute atom concentration in Al matrix compared to annealing treatment. High-pressure torsion at 200 °C has been demonstrated as a new and effective way for obtaining combination of high mechanical strength and electrical conductivity in Al–Fe alloys.The dynamic aging of UFG Al–Fe alloy (HPT at 200 °C) has been used to enhance the electrical conductivity. Comparison of observed results with static aging (annealing at 200 °C for 8 h), also performed in present work, shows superiority of dynamically aged alloy over statically aged. The increase of electrical conductivity by ≈3% IACS is accompanied by substantial decrease of heat treatment time from 8 h for static annealing to 5 min for high temperature deformation.
      PubDate: 2017-11-20T02:50:28.962728-05:
      DOI: 10.1002/adem.201700867
       
  • Microstructure and Texture Development in Al–3%Brass Composite
           Produced through ARB
    • Authors: Ehsan Tolouei; Mohammad Reza Toroghinejad, Hamed Asgari, Hossein Monajati Zadeh, Fakhreddin Ashrafizadeh, Jerzy A. Szpunar, Philippe Bocher
      Abstract: In the present work, aluminum-3% brass composite sheets are produced by accumulative roll bonding (ARB) process up to nine passes at ambient temperature. Evolution of rolling texture is studied by texture measurement using X-ray diffraction method. The results show that ARB process leads to the formation of copper ({112} ) and Dillamore ({4 4 11} ) as the major texture components. The intensity of copper and Dillamore components enhances to values as high as 19 times that of random with increasing number of passes to 9. It is observed that the 5th pass is a transition in development of the texture components, after which the intensities undergo a drop. The textures are comparable to ARB process of high purity aluminum, indicating that the addition of 3% brass particles do not cause any significant change in the deformation behavior. Electron backscatter diffraction (EBSD) technique is used to examine the microstructure; the results reveal formation of ultrafine grains (UFG), starting in the 3rd pass and covers the entire structure after the 5th pass. The major mechanisms involved are identified as rotation of the sub-grains, as well as grain boundary migration.Aluminum–brass composite is produced by ARB process up to nine passes. Recrystallization and formation of new grains start from the 3rd pass and continues to the 7th pass. Intensity of the textures decreases after recrystallization; Dillamore and Copper components are the main textures of the composite.
      PubDate: 2017-11-17T02:31:33.642186-05:
      DOI: 10.1002/adem.201700463
       
  • An Evaporative Initiated Chemical Vapor Deposition Coater for Nanoglue
           Bonding
    • Authors: Greg C. Randall; Luis Gonzalez, Ron Petzoldt, Fred Elsner
      Abstract: The authors present an evaporative initiated chemical vapor deposition (iCVD) coater and use it to establish a submicron bonding process for millimeter-scale foils with potentially rough surface features. The coater uses a simple benchtop design suited to research labs, with pre-heated metal pins instead of hot filaments, and direct evaporation of reactants within the chamber. Coatings of poly(glycidyl methacrylate) (pGMA) with thickness 100–800 nm are achieved at rates of 10–40 nm min−1 on substrates common in high energy laser compression experiments. Coating uniformities of 10–30 nm mm−1 are demonstrated in a ≈60 × 10 mm zone under the heated pins. As an aside, the authors further show the ability to coat intentionally non-uniform layers in a monomer vapor diffusion gradient. Coatings are formed on both plastics and solids ranging from smooth, non-burred silicon or lithium fluoride to rough and burred metals (aluminum and copper). These coated substrates are then chemically bonded under mild heat and pressure. Detailed surface, thickness, and cross-sectional characterization is performed to confirm a submicron bond gap and to troubleshoot the common clearance issues from burrs, roughness, and surface curvature. Peeling and dropping bond strength tests confirm the bonds are robust, when coated and assembled under conditions to mitigate clearance issues.A simplified evaporative initiated chemical vapor deposition (iCVD) coater is developed for submicron bond gaps in materials with potentially imperfect surfaces. A robust bonding process is designed to overcome the most common irregular surface features (curvature, roughness, and burrs) followed from contact elasticity analysis. Bond gaps of 0.2–1.5 µm are achieved in combinations of common plastics, metals, and ceramic-like foils.
      PubDate: 2017-11-16T10:00:30.304446-05:
      DOI: 10.1002/adem.201700839
       
  • Nanometer-Thick Ionic Liquids as Boundary Lubricants
    • Authors: Xiao Gong; Lei Li
      Abstract: Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. Due to high thermal stability and promising tribological properties, there have been increasing research interests in applying ILs as boundary lubricants. In this review, the authors will discuss the recent progress on this topic with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties. First, the fundamentals on boundary lubrication and the state-of-the-art lubricants will be reviewed briefly. Second, the progress on the molecular structure of ILs confined to a solid surface will be discussed. Afterward, the experimental and computational efforts on the ILs as boundary lubricants will be discussed in details with emphasis on the effect of IL structure, solid substrates, and IL-soild interaction. Finally, the future research directions will be discussed.Ionic liquids (ILs) are fascinating materials with unique combination of solid and liquid properties. In this review, we discuss the recent progress on their potential application as boundary lubricants with the emphasis on the relationship between the molecular arrangement of ILs confined to a solid and the tribological properties.
      PubDate: 2017-11-15T11:58:30.954432-05:
      DOI: 10.1002/adem.201700617
       
  • Diversity in Addressing Reaction Mechanisms of Nano-Thermite Composites
           with a Layer by Layer Structure
    • Authors: Hongtao Sui; Lauren LeSergent, John Z. Wen
      Abstract: The reaction mechanisms and microstructures of various layered nano-thermite composites are investigated through characterization of their energetic properties. Migration of reactive components across the reaction zone is analyzed, which plays an important role in determining the process initiation, reaction propagation, and chemical stability at low temperatures. Distinct types of nanoparticles are deposited onto filter paper in a sequence, using the vacuum filtration method, which promotes intimate contact between neighboring reactive layers. Scanning Electron Microscopy (SEM) images demonstrate a well-defined contact region between the two layers in the Al/CuO or Al/NiO composites. Differential Scanning Calorimetry (DSC) data shows that the thermite reaction occurs below the melting temperature of Al, resulting in rapid heat release, and improves reaction initiation. Elemental mapping results reveal the migration of Al, Ni/Cu, and oxygen before and after the thermite reaction, which is arranged during thermogravimetric analysis (TGA). This analysis indicates the dominant pathway of the thermite reaction in each composite, through either decomposition of the CuO nanoparticles in the Al/CuO composite or through direct migration of reactive components across the conducting surface within the Al/NiO composite.Layer-by-layer structured Al–CuO and Al–NiO nanoparticles are investigated via characterization of their microstructures and elemental mapping. Experimental data indicates for Al–CuO the reaction involves decomposition of CuO into oxygen, while for Al–NiO migration of reactive species across the conducting surface is critical.
      PubDate: 2017-11-15T11:57:02.787975-05:
      DOI: 10.1002/adem.201700822
       
  • 3D Printing of Diamond Tools for Dental Ceramics Processing
    • Authors: Zhibo Yang; Junchen Hu, Kaiqiang Li, Aiju Liu, Shian Liu
      Abstract: This paper is focused on preparing diamond tools with orderly arranged abrasive particles for dental ceramics processing via 3D printing. This allows one to overcome such drawbacks of the existing methods of dental ceramics processing as weak bonding strength, short service life, and irregular diamond distribution in diamond tools. Firstly, the CAD model of the dental diamond tool is constructed using 3D cartographic software, with level-scan-path geometry information generated via hierarchcal slicing. Then, using Ni–Cr alloy powder and diamond as raw materials, the dental ceramics processing diamond tool with orderly arranged diamond particles is prepared via a 3D printer. Next, an X-ray diffractometer, energy dispersive spectrometer, and scanning electron microscope are used to analyze the microstructure of the Ni–Cr alloy and diamond particle interfaces, resulting in the identification of their bonding mechanism. Finally, the diamond grinding wheel produced by 3D printing is subjected to dental zirconia ceramics grinding performance tests. The results obtained confirm that diamond particles experience normal wear, while no abrasive falling off occurs on the 3D printed diamond tool surface.In this paper, diamond tools for dental ceramics processing are manufactured using the 3D printing technology. Laser fast scanning is utilized to make the 3D distribution of diamond particles more regular, thus, significantly improving the manufacturing performance of grinding wheels.
      PubDate: 2017-11-15T11:56:27.324339-05:
      DOI: 10.1002/adem.201700747
       
  • Smart Energetics: Sensitization of the Aluminum-Fluoropolymer Reactive
           System
    • Authors: Sara L. Row; Lori J. Groven
      Abstract: The development of smart energetics is at the forefront of the research community. The desire is to have energetics that could have ON/OFF capability, tunable performance, and/or targeted energy delivery. Therefore, efforts have been focused on designing systems that respond to stimuli in a controlled manner. In this paper, nanoscale aluminum (nAl)/fluoropolymer reactive systems are studied and the piezoelectric nature of the fluoropolymers is used as a means to sensitize the system. Using a capacitor type setup, and drawing on our previous efforts, three fluoropolymer/nAl systems are studied and their sensitivities upon application of a DC voltage are quantified using BAM drop weight as the indicator. It is found, upon application of 1.0 kV, that for all three fluoropolymer/Al systems the sensitivity is greatly increased. For example, for the THV221/nAl system the impact energy required for ignition is reduced from 63 to 10 J. Further increasing the applied voltage is shown to further increase the sensitivity for all systems studied. The role of electroactive phase content and sensitization time is also discussed.Aluminum/fluoropolymer reactives are formulated and demonstrate switchable behavior upon application of a DC voltage. The drop weight sensitivity is on par with powdered RDX and PETN. This demonstrates that piezoelectric fluoropolymer bound reactives could be developed into smart energetics.
      PubDate: 2017-11-14T12:50:22.264431-05:
      DOI: 10.1002/adem.201700409
       
  • Impact of Cement Hydration on Durability of Cellulosic Fiber-Reinforced
           Cementitious Composites in the Presence of Metakaolin
    • Authors: Jianqiang Wei
      Abstract: Degradation of cellulosic fiber in the alkaline environment of concrete generated in the process of cement hydration is the primary reason for the low durability of such composites. However, the impact of cement hydration on cellulosic fiber's degradation in cementitious systems has not been thoroughly understood. This paper presents the dependence of deterioration behavior of cellulosic fiber-cement systems on cement hydration in the presence of metakaolin. Experimental investigations, such as isothermal calorimetry, thermogravimetric analysis and energy dispersive X-ray spectroscopy, and thermodynamic simulations are carried out to investigate cement hydration kinetics and hydration products. Durability of cellulosic fiber-reinforced cement composite is assessed based on the degradation in flexural properties. The results indicate that, in the presence of metakaolin, the hydration of cement is enhanced accompanied by consumption of calcium hydroxide, low release of hydration heat, decreased Ca/Al and Ca/Si ratios of C–S–H phase, and reduced OH- and Ca2+ amounts in pore solution. A cement substitution by 30 wt% metakaolin results in an improvement of flexural toughness and durability of cellulosic fiber-reinforced cement composites by 42 and 269%, respectively. The correlations between composite durability and hydration of Portland cement are established.Hydration of cement is identified as a crucial factor in understanding the deterioration behavior of cellulosic fibers-reinforced cementitious composites. Effect of metakaolin, on durability of cellulosic fiber-reinforced cement composites are evaluated by means of degradation in flexural properties. Based on the experimental and simulation observations, correlations between durability of cellulosic fiber-cement system and cement chemistry are established.
      PubDate: 2017-11-14T02:27:19.086803-05:
      DOI: 10.1002/adem.201700642
       
  • Production and Anisotropic Tensile Behavior of Resin-Metal
           Interpenetrating Phase Composites
    • Authors: Zhaoyao Zhou; Bibo Yao, Liuyang Duan, Jie Qin
      Abstract: Metal-polymer composites can be used to synthesize material properties. A variety of interpenetrating phase composites have been produced by spontaneously infiltrating porous short-fiber preforms with unsaturated polyester resin under vacuum conditions. Porous preforms are fabricated by compacting and sintering short 304 stainless steel fibers from cutting stainless steel fiber ropes. Tensile experiments are conducted, and fractographs are examined via scanning electron microscopy. The results reveal that the tensile strength, elongation at maximum stress, and elasticity modulus of the IPCs increase with the increasing fiber fractions and exhibit anisotropy in different directions. The tensile strength and elongation at maximum stress are significantly improved compared with the consistent preforms. A nonlinear elastic behavior and sawtooth-like fluctuation during yield deformation are noted. Compared with the through-thickness direction, a higher tensile strength and larger elongation at maximum stress are observed in the in-plane direction. Finer-diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characteristics.Metal-resin IPCs are produced by vacuum-infiltration of unsaturated polyester resin into the stainless steel preforms and their tensile properties are analyzed. The tensile strength and elongation at maximum stress increase with the increasing fiber fractions and exhibit anisotropy. Finer diameter fibers can improve the strength and increase the elongation at maximum stress. The tensile fracture surfaces show a mixture of brittle and plastic fracture characterizations.
      PubDate: 2017-11-14T02:25:36.705722-05:
      DOI: 10.1002/adem.201700669
       
  • Influence of Ingot and Powder Metallurgy Production Route on the Tensile
           Creep Behavior of Mo–9Si–8B Alloys with Additions of Al and Ge
    • Authors: P. M. Kellner; R. Völkl, U. Glatzel
      Abstract: Refractory metals and their alloys show potential for high temperature applications, due to the elevated melting points often paired with very good creep resistance. Spark plasma sintering (SPS) as well as arc-melting is used here to prepare quaternary and quinternary Mo–9Si–8B–xAl–yGe (x is 0 or 2; y is 0 or 2, all numbers in at%) samples. All samples consist of a Mo solid solution (Moss) and two intermetallic phases: Mo3Si (A15) and Mo5SiB2 (T2). Aluminum and germanium reduce the melting point and slightly decrease the density of the material. The specimens are homogenized and coarsened by a subsequent heat-treatment in vacuum at 1850 °C for 24 h. The resulting microstructure is investigated using scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and inductively coupled plasma optical emission spectrometry (ICP-OES) analysis. A vacuum creep testing device for small tensile creep specimens is presented. It is heated by graphite radiation heaters usable up to 1500 °C in vacuum of 2 · 10-4 Pa with an oil diffusion pump. Tensile creep tests are performed at 1250 °C and stresses from 50 MPa up to 250 MPa. Specimens produced by ingot metallurgy feature superior creep properties compared to powder metallurgy samples.In this study, tensile creep tests are performed for Mo–Si–B alloys at 1250 °C and stresses from 50 to 250 MPa manufactured by argon arc melting and powder metallurgy. Specimens produced by argon arc melted feature superior creep properties compared to powder metallurgy ones, due to grain size.
      PubDate: 2017-11-13T02:46:55.570691-05:
      DOI: 10.1002/adem.201700751
       
  • Stress Reduction of 3D Printed Compliance-Tailored Multilayers
    • Authors: Shanmugam Kumar; Brian L. Wardle, Muhamad F. Arif, Jabir Ubaid
      Abstract: Multilayered multi-material interfaces are encountered in an array of fields. Here, enhanced mechanical performance of such multi-material interfaces is demonstrated, focusing on strength and stiffness, by employing bondlayers with spatially-tuned elastic properties realized via 3D printing. Compliance of the bondlayer is varied along the bondlength with increased compliance at the ends to relieve stress concentrations. Experimental testing to failure of a tri-layered assembly in a single-lap joint configuration, including optical strain mapping, reveals that the stress and strain redistribution of the compliance-tailored bondlayer increases strength by 100% and toughness by 60%, compared to a constant modulus bondlayer, while maintaining the stiffness of the joint with the homogeneous stiff bondlayer. Analyses show that the stress concentrations for both peel and shear stress in the bondlayer have a global minimum when the compliant bond at the lap end comprises ≈10% of the bondlength, and further that increased multilayer performance also holds for long (relative to critical shear transfer length) bondlengths. Damage and failure resistance of multi-material interfaces can be improved substantially via the compliance-tailoring demonstrated here, with immediate relevance in additive manufacturing joining applications, and shows promise for generalized joining applications including adhesive bonding.By crafting a spatially compliance-tailored bondlayer utilizing additive manufacturing, mechanical performance can be increased significantly compared to the homogeneous stiff or compliant bondlayer, imparting greater strength, strain to break, and toughness, while maintaining stiffness of the homogeneous stiff bondlayer.
      PubDate: 2017-11-08T08:15:47.562197-05:
      DOI: 10.1002/adem.201700883
       
  • Fabrication and Optical Properties of Periodic Ag Nano-Pore and
           Nano-Particle Arrays with Controlled Shape and Size over Macroscopic
           Length Scales
    • Authors: Colm T. Mallon; Kiang W. Kho, Houda Gartite, Robert J. Forster, Tia E. Keyes
      Abstract: A facile and economical route to preparation of highly ordered sliver pore or particle arrays with controlled pore-shape and size extended over cm2 areas is described. The substrates are prepared at planar and curved surfaces via sphere-imprinted polymer (PDMS) templating using polystyrene spheres with diameters of 820, 600, or 430 nm. Nano-pore arrays are created by sputtering 80 nm of Ag directly onto the templates and nano-particle arrays are prepared by electrode-less deposition of Ag from Tollen's reagent. The shape of the nano-pore or particles in the array conformed to that of the imprint of the sphere on the template. Stretching the flexible template enable creation of cuboid shaped nano-voids and nano-particles following Ag deposition. Diffuse reflectance from the spherical Ag nano-cavity arrays showed absorbance maxima at wavelengths comparable similar to the diameter of the templating sphere, whereas reflectance from the cuboid arrays, showed little correlation with the sphere diameter. The cuboid nano-particle arrays showed the most intense visible absorption which is red-shifted compared to the spherical arrays. White light diffraction from the arrays, observed by rotating 1 cm2 substrates relative to a fixed light source, reflected exactly the symmetry axes of the periodic nano-features in the arrays demonstrating the remarkable macroscopic order of the periodic structures. Raman spectra of 1-benzenethiol adsorbed at the arrays indicated SERS enhancements from the substrates are attributed mainly to surface nano-roughness with only moderate contributions from the periodically corrugated structures. Despite excitation at the major resonance dip in the reflectance spectrum, a weak, localized rim dipole mode is found to elicit a small increase in the SERS enhancement factor for the 430 nm diameter spherical arrays. FDTD studies of nano-void arrays provided insights into various factors affecting the SERS experiment and confirmed the array's plasmonic spectra are dominated by propagating plasmon modes under microscope excitation/collection angles.In this paper, a facile and economical route to preparation of highly ordered silver nano-pore arrays via sphere imprinted PDMS templating is described. We demonstrated that a series of various pore-shapes, ranging from spherical and cuboid, can be obtained by stretching the polymer template. FDTD simulation is also carried out to provide insights into the plasmonic origin of the observed SERS enhancements.
      PubDate: 2017-10-24T11:53:03.324955-05:
      DOI: 10.1002/adem.201700532
       
  • High-Entropy Alloys: Potential Candidates for High-Temperature
           Applications – An Overview
    • Authors: Sathiyamoorthi Praveen; Hyoung Seop Kim
      Abstract: Multi-principal elemental alloys, commonly referred to as high-entropy alloys (HEAs), are a new class of emerging advanced materials with novel alloy design concept. Unlike the design of conventional alloys, which is based on one or at most two principal elements, the design of HEA is based on multi-principal elements in equal or near-equal atomic ratio. The advent of HEA has revived the alloy design perception and paved the way to produce an ample number of compositions with different combinations of promising properties for a variety of structural applications. Among the properties possessed by HEAs, sluggish diffusion and strength retention at elevated temperature have caught wide attention. The need to develop new materials for high-temperature applications with superior high-temperature properties over superalloys has been one of the prime concerns of the high-temperature materials research community. The current article shows that HEAs have the potential to replace Ni-base superalloys as the next generation high-temperature materials. This review focuses on the phase stability, microstructural stability, and high-temperature mechanical properties of HEAs. This article will be highly beneficial for materials engineering and science community whose interest is in the development and understanding of HEAs for high-temperature applications.In recent years, high entropy alloys (HEAs) receive wide attention due to its unique alloy design concept and outstanding properties. This review presents a general overview of HEAs as a potential candidate for high-temperature applications. The need for the profound research on the high-temperature properties of HEAs is highlighted.
      PubDate: 2017-10-18T06:35:39.302184-05:
      DOI: 10.1002/adem.201700645
       
  • Rationally Designed Silicon Nanostructures as Anode Material for
           Lithium-Ion Batteries
    • Authors: Tong Shen; Zhujun Yao, Xinhui Xia, Xiuli Wang, Changdong Gu, Jiangping Tu
      Abstract: Silicon (Si) is promising for high capacity anodes in lithium-ion batteries due to its high theoretical capacity, low working potential, and natural abundance. However, there are two main drawbacks that impede its further practical applications. One is the huge volume expansion generating during lithiation and delithiation progresses, which leads to severe structural pulverization and subsequently rapid capacity fading of the electrode. The other is the relatively low intrinsic electronic conductivity, therefore, seriously impacting the rate performance. In the past decades, numerous efforts have been devoted for improving the cycling stability and rate capability by rational designs of different nanostructures of Si materials and incorporations with some conductive agents. In this review, the authors summarize the exciting recent research works and focus on not only the synthesis techniques, but also the composition strategies of silicon nanostructures. The advantages and disadvantages of the nanostructures as well as the perspective of this research field are also discussed. We aim to give some reference for engineering application on Si anodes in lithium ion batteries.The authors summarize the strategies that developed lately for improving the electrochemical performance of Si materials. Special focus in this review is the recent progresses in the rational fabrication of Si nanostructures with multiple morphologies, including nanoparticles, nanowires, thin films, and porous structures. Moreover, further improvement tactics, such as collaborating with carbonaceous materials, conductive polymers, and alloy materials are also discussed.
      PubDate: 2017-10-05T08:32:53.56802-05:0
      DOI: 10.1002/adem.201700591
       
  • Porous Polymer Membranes by Hard Templating – A Review
    • Authors: Mario Stucki; Michael Loepfe, Wendelin J. Stark
      Abstract: Membranes are designed to bridge a precise separation process at the nanoscale with industrial applications running at cubic meters per hour. This review outlines materials applied in membrane production with a particular focus on polymers. Membrane performance and created value are directly linked to controlled pore formation. Their economic relevance has created a number of large companies and associated academic research at top institutions. The authors review, therefore, starts from well-established techniques applied in products and then moves on to evolving concepts from academia. Pore formation through hard templating is a versatile field for separation processes. A more detailed view is given on the two known concepts for nanopore formation, namely colloidal templates and random hard salt templating. A comparison between these two concepts underlines their relevance to combine a process specific separation with large scale manufacturing requirements (i.e., upscale possibility, flexible process control and environmental impact).Membranes bridge nanoscale separation with high volume throughput. The development of membranes has resulted in a large variety of materials used for porous separators. This article introduces the relevant membrane processes and focuses on porous polymer membranes. Its main body explains sacrificial hard templating. Ordered colloidal crystals are compared to random templates with respect to their scalability and application.
      PubDate: 2017-09-28T00:05:53.544922-05:
      DOI: 10.1002/adem.201700611
       
  • High-Entropy Alloy (HEA)-Coated Nanolattice Structures and Their
           Mechanical Properties
    • Authors: Libo Gao; Jian Song, Zengbao Jiao, Weibing Liao, Junhua Luan, James Utama Surjadi, Junyang Li, Hongti Zhang, Dong Sun, Chain Tsuan Liu, Yang Lu
      Abstract: Nanolattice structure fabricated by two-photon lithography (TPL) is a coupling of size-dependent mechanical properties at micro/nano-scale with structural geometry responses in wide applications of scalable micro/nano-manufacturing. In this work, three-dimensional (3D) polymeric nanolattices are initially fabricated using TPL, then conformably coated with an 80 nm thick high-entropy alloy (HEA) thin film (CoCrFeNiAl0.3) via physical vapor deposition (PVD). 3D atomic-probe tomography (APT) reveals the homogeneous element distribution in the synthesized HEA film deposited on the substrate. Mechanical properties of the obtained composite architectures are investigated via in situ scanning electron microscope (SEM) compression test, as well as finite element method (FEM) at the relevant length scales. The presented HEA-coated nanolattice encouragingly not only exhibits superior compressive specific strength of ≈0.032 MPa kg−1 m3 with density well below 1000 kg m−3, but also shows good compression ductility due to its composite nature. This concept of combining HEA with polymer lattice structures demonstrates the potential of fabricating novel architected metamaterials with tunable mechanical properties.High entropy alloy (HEA)-coated nanolattice structures with tunable mechanical properties have been developed, with the characteristics feature sizes spanning from 5 nm to 20 μm.
      PubDate: 2017-09-20T03:11:21.139452-05:
      DOI: 10.1002/adem.201700625
       
  • Hydrogen Trapping in Some Automotive Martensitic Advanced High-Strength
           Steels
    • Authors: Jeffrey Venezuela; Qingjun Zhou, Qinglong Liu, Mingxing Zhang, Andrej Atrens
      Abstract: Hydrogen permeation experiments are used to investigate hydrogen trapping in commercial automotive martensitic advanced high-strength steels. Hydrogen trapping increases with increasing mechanical strength, as indicated by (i) the decrease in the hydrogen diffusion coefficient, and (ii) the increase in reversible hydrogen trap density. The measured trap densities are in the order of ≈1017– ≈ 1018 cm−3. The relationship between trapping characteristics and HE susceptibility of MS-AHSS is discussed in terms of Hydrogen Enhanced Macroscopic Plasticity (HEMP) and Hydrogen Assisted Micro-fracture (HAM).Reversible trapping of hydrogen by dislocations may explain the hydrogen-influenced behavior in the MS-AHSS: (i) the reduction of the yield strength by the Hydrogen Enhanced Macroscopic Plasticity (HELP) mechanism, and (ii) the occurrence of shear micro-fracture by the Hydrogen Assisted Micro-fracture (HAM) mechanism.
      PubDate: 2017-09-13T13:02:10.393178-05:
      DOI: 10.1002/adem.201700468
       
  • Threshold Fluence Measurement for Laser Liftoff of InP Thin Films by
           Selective Absorption
    • Authors: Antony Jan; Benjamin A. Reeves, Yoeri van de Burgt, Garrett J. Hayes, Bruce M. Clemens
      Abstract: We explore conditions for achieving laser liftoff in epitaxially grown heterojunctions, in which single crystal thin films can be separated from their growth substrates using a selectively absorbing buried intermediate layer. Because this highly non-linear process is subject to a variety of process instabilities, it is essential to accurately characterize the parameters resulting in liftoff. Here, we present an InP/InGaAs/InP heterojunction as a model system for such characterization. We show separation of InP thin films from single crystal InP growth substrates, wherein a ≈10 ns, Nd:YAG laser pulse selectively heats a coherently strained, buried InGaAs layer. We develop a technique to measure liftoff threshold fluences within an inhomogeneous laser spatial profile, and apply this technique to determine threshold fluences of the order 0.5 J cm−2 for our specimens. We find that the fluence at the InGaAs layer is limited by non-linear absorption and InP surface damage at high powers, and measure the energy transmission in an InP substrate from 0 to 8 J cm−2. Characterization of the ejected thin films shows crack-free, single crystal InP. Finally, we present evidence that the hot InGaAs initiates a liquid phase front that travels into the InP substrate during liftoff.In epitaxial laser liftoff, the selective absorption of a bright laser pulse by a buried layer results in the separation of the thin film above it from the substrate below, as shown in the accompanying figure. The wafer can be washed and reused for growth, lowering device costs. The resulting films are single crystal and crack free.
      PubDate: 2017-09-11T10:26:16.695208-05:
      DOI: 10.1002/adem.201700624
       
  • Grain Refinement through Shear Banding in Severely Plastic Deformed A206
           Aluminum Alloy
    • Authors: Parya Teymoory; Abbas Zarei-Hanzaki, Ehsan Farabi, Hossein Monajati, Hamid Reza Abedi
      Abstract: The present work is conducted to study the microstructure and texture evolutions in an as-cast A206 aluminum alloy after applying severe plastic deformation. Toward this end, the material is severely deformed through accumulative back extrusion (ABE) technique at 200 °C and followed by assessing the room temperature mechanical properties of the products. The macro shear-bands formation in the highly strained regions can result in grain refinement through the geometric dynamic recrystallization mechanism. A significant refinement is also characterized within the micro shear-bands; this is attributed to the intensified substructure development and the occurrence of continuous dynamic recrystallization. The corresponding inverse pole figure maps show similar orientation for these newly refined grains with the parent ones. A random texture is produced through sub-grain rotation to dissimilar orientation at the intersection of micro-bands. The assessment of mechanical properties of the processed materials reveal significant increase in both yield and ultimate tensile strength values. The hardness profiles also demonstrate a relatively homogenous microstructure after three and five ABE passes holding a mean hardness value of 183 Vickers.A206 alloy is severely deformed by accumulative back extrusion (ABE) technique at 200 °C and then the room temperature mechanical properties of the products are scrutinized. Enhancement of these properties is attributed to grain refinement that is caused by the presence of micro and macro-shear bands in the heavily deformed regions of the material.
      PubDate: 2017-09-11T01:46:20.782144-05:
      DOI: 10.1002/adem.201700502
       
  • Influence of Stress-Aging Processing on Precipitates and Mechanical
           Properties of a 7075 Aluminum Alloy
    • Authors: Y. C. Lin; Yu-Qiang Jiang, Jin-Long Zhang, Xiao-Min Chen
      Abstract: Two-step stress-aging tests, as well as pre-treatment plus stress-aging experiments, are performed on a 7075 aluminum (Al–Zn–Mg–Cu) alloy. Influences of stress-aging parameters on mechanical behavior and fracture mechanism are investigated through uniaxial tensile test and fracture morphology analysis. It is revealed that the stress-aging dramatically influences the mechanical properties and fracture characteristics of the studied alloy, which is contributed to the sensitivity of microstructures to stress-aging. When the alloy undergoes two-step stress-aging, the ultimate tensile strength and yield strength first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. For the retrogression pre-treated plus stress-aged alloy, the yield strength first increases and then drops with the increased retrogression pre-treatment time, while the ultimate tensile strength almost remains stable. Furthermore, the elongation continuously increases with the increased retrogression pre-treatment time. The observation of fracture morphology indicates that the dimple-type intergranular fracture is the main fracture mechanism for the two-step stress-aged and retrogression pre-treated plus stress-aged alloys.Effects of stress-aging on mechanical behavior and fracture mechanisms of an Al–Zn–Mg–Cu alloy are investigated. It is found that the mechanical strengths of the two-step stress-aged alloy first increase and then decrease with the increased first step stress-aging temperature, while the elongation first decreases and then increases. The dimple-type intergranular fracture is the main fracture mechanism for stress-aged alloys.
      PubDate: 2017-09-07T08:00:52.278529-05:
      DOI: 10.1002/adem.201700583
       
  • Equivalent Hydrogen Fugacity during Electrochemical Charging of 980DP
           Steel Determined by Thermal Desorption Spectroscopy
    • Authors: Qinglong Liu; Evan Gray, Jeffrey Venezuela, Qingjun Zhou, Clotario Tapia-Bastidas, Mingxing Zhang, Andrej Atrens
      Abstract: Thermal desorption spectroscopy (TDS) is used to analyze hydrogen in 980DP after (i) electrochemical charging, and (ii) gaseous charging. The hydrogen concentration increases with (i) a more negative charging potential and (ii) an increasing hydrogen gas pressure. For charging in 0.1 M NaOH, the hydrogen fugacity for 980DP is similar to that for (i) low interstitial steel, and (ii) MS1500, and is greater than that for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry on the hydrogen evolution reaction. The de-trapping activation energies are 40.5 and 50.2 kJ mol−1, indicating hydrogen traps at boundary defects.The figure shows that, for cathodic hydrogen charging in 0.1 M NaOH, the hydrogen fugacity is similar for the (i) 980DP steel (ii) low interstitial steel, and (iii) MS1500, and was greater than the fugacity for the 3.5NiCrMoV steel. This indicates an influence of steel chemistry, most likely, on the details of the hydrogen evolution reaction.
      PubDate: 2017-09-07T07:41:18.465735-05:
      DOI: 10.1002/adem.201700469
       
  • Mechanical Properties, Fatigue Life, and Electrical Conductivity of
           Cu–Cr–Hf Alloy after Equal Channel Angular Pressing
    • Authors: Daria V. Shangina; Vladimir F. Terent'ev, Dmitry V. Prosvirnin, Olga V. Antonova, Natalia R. Bochvar, Mikhail V. Gorshenkov, Georgy I. Raab, Sergey V. Dobatkin
      Abstract: Structure, mechanical, and service properties of a Cu–Cr–Hf alloy after quenching, equal-channel angular pressing (ECAP), and subsequent aging have been studied. The positive effects of ultrafine-grained structure formation (grain/subgrain size of ≈200 nm) during ECAP and strengthening particles precipitation upon subsequent aging at 450 °C on the mechanical and fatigue properties of the alloy are shown. Ultrafine-grained Cu–Cr–Hf alloy after aging shows increasing in the fatigue limit on the basis of 107 cycles from 185 to 375 MPa relative to that of the initial coarse-grained state. The alloy after ECAP and aging also exhibits sufficient elongation to failure (11.4%) and good electrical conductivity (78%IACS).Mechanical and service properties of a Cu–Cr–Hf alloy after equal channel angular pressing (ECAP) and aging have been studied. The positive effects of ultrafine-grained structure and precipitates on the tensile and fatigue properties of the material are shown. The alloy after ECAP and aging exhibits sufficient elongation and good electrical conductivity.
      PubDate: 2017-09-05T07:06:54.713546-05:
      DOI: 10.1002/adem.201700536
       
  • Uniting Strength and Toughness of Al Matrix Composites with Coordinated
           Al3Ni and Al3Ti Reinforcements
    • Authors: Frederick M. Heim; Yunya Zhang, Xiaodong Li
      Abstract: Hybrid aluminum composites are fabricated in a novel manner to characteristically induce a layer-wise aligned distribution of micro-scale Al3Ni and Al3Ti intermetallic particles that are formed in situ within a ductile Al matrix. The simple and unique Rolling of Randomly Orientated Layer-wise Materials (RROLM) manufacturing methodology enables microstructural tailoring of the intermetallic reinforcing particles to prescribe enhanced crack tip deflection caused by the complex interaction of local veins of reinforcement particles, in an effort to overshadow the classical loss of toughness in large-particle reinforced composites. The complimentary reinforcements and their interface with the Al matrix are revealed to have a gradual transition zone that functions to maintain critical cohesion with the particles and the matrix, empowering the superior load transfer capability of the particles, and reducing microvoid penetration into the matrix. In situ three-point bending observations combined with a local strain field analysis, demonstrate the distinctive crack deflection mechanisms exhibit by the composite. Deviating from the norm, this specialized particle reinforced composite exhibited both strengthening and toughening mechanisms simultaneously, over control samples. The investigated design strategy and model material will assist materials development toward light-weight, stronger, and tougher particle reinforced Al matrix composites.Specialized aluminum matrix composites microstructurally tailored with coordinated dual intermetallic reinforcement particles have been developed though a simple, yet original, methodology, which is specifically designed to enhance toughness and strength simultaneously. Bi-level microcracking and crack tip deflection are expected to have enabled the improved toughness. Hybrid materials like these are anticipated to enable future designs.
      PubDate: 2017-09-05T07:06:25.40406-05:0
      DOI: 10.1002/adem.201700605
       
  • Current Status and Recent Developments in Porous Magnesium Fabrication
    • Authors: Alicja Kucharczyk; Krzysztof Naplocha, Jacek W. Kaczmar, Hajo Dieringa, Karl U. Kainer
      Abstract: A significant number of studies have been dedicated to the fabrication and properties of metallic foams. The most recent research is focused on metals with low weight and good mechanical properties, such as titanium, aluminum, and magnesium. Whereas the first two are already fairly well studied and already find application in industry, magnesium currently remains at the research stage. The present review covers the studies conducted on fabrication techniques, surface modifications, and properties of porous structures made of magnesium and its alloys.Magnesium foams attract more and more interest due to their low weight, material availability, and mechanical properties. However, due to the flammability and reactivity of magnesium, not all metallic foam manufacturing methods can be used. Therefore, the article summarizes the latest production methods and modifications of already existing ones as well as information about mechanical properties and corrosion resistance.
      PubDate: 2017-09-05T07:00:47.509733-05:
      DOI: 10.1002/adem.201700562
       
  • Sliding and Migration of Tilt Grain Boundaries in a Mg–Zn–Y
           Alloy
    • Authors: Weiwei Hu; Zhiqing Yang, Hengqiang Ye
      Abstract: Sliding and migration of tilt grain boundaries in a Mg–Zn–Y alloy have been investigated on the atomic scale using aberration-corrected scanning transmission electron microscopy. Grain boundary sliding is accommodated by non-basal dislocations moving along the grain boundary; grain boundary migration is induced by the motion of grain boundary dislocations with synchronized grain boundary diffusion. Simultaneous sliding and migration of tilt boundaries take place in both Mg matrix and long period stacking ordered phases. These results provide evidence for occurrence of grain boundary motion, which may play a role in plasticity of this kind of Mg alloys.Tilt grain boundaries are formed widely as a result of basal slip in Mg alloys. Sliding and migration of tilt grain boundaries take place in both Mg matrix and long period stacking ordered phases in a Mg–Zn–Y alloy. Sliding and migration of tilt grain boundaries accommodated by non-basal dislocations or grain boundary dislocations motion may play important roles in formability of high-strength Mg alloys.
      PubDate: 2017-09-05T07:00:33.282776-05:
      DOI: 10.1002/adem.201700516
       
  • Effects of Multi-Scale Patterning on the Run-In Behavior of
           Steel–Alumina Pairings under Lubricated Conditions
    • Authors: Philipp G. Grützmacher; Andreas Rosenkranz, Adam Szurdak, Carsten Gachot, Gerhard Hirt, Frank Mücklich
      Abstract: In nature, many examples of multi-scale surfaces with outstanding tribological properties such as reduced friction and wear under dry friction and lubricated conditions can be found. To determine whether multi-scale surfaces positively affect the frictional and wear performance, tests are performed on a ball-on-disk tribometer under lubricated conditions using an additive-free poly-alpha-olefine oil under a contact pressure of around 1.29 GPa. For this purpose, stainless steel specimens (AISI 304) are modified by micro-coining (hemispherical structures with a structural depth of either 50 or 95 μm) and subsequently by direct laser interference patterning (cross-like pattern with 9 μm periodicity) to create a multi-scale pattern. The comparison of different sample states (polished reference, laser-patterned, micro-coined, and multi-scale) shows a clear influence of the fabrication technique. In terms of the multi-scale structures, the structural depth of the coarser micro-coining plays an important role. In case of lower coining depths (50 μm), the multi-scale specimens show an increased coefficient of friction compared to the purely micro-coined surfaces, whereas larger coining depths (95 μm) result in stable and lower friction values for the multi-scale patterns.The tribological effects of a multi-scale surface patterning technique are investigated. Steel specimens (AISI 304) are modified by micro-coining and subsequently by direct laser interference patterning to create a multi-scale pattern. Depending on the depth of the coined structures, the multi-scale patterns have positive (deep coined-structures) or negative frictional effects (shallow coined structures).
      PubDate: 2017-09-01T14:36:21.552081-05:
      DOI: 10.1002/adem.201700521
       
  • Electrically Assisted Ultrasonic Nanocrystal Surface Modification of
           Ti6Al4V Alloy
    • Authors: Jun Liu; Sergey Suslov, Shengxi Li, Haifeng Qin, Zhencheng Ren, Gary L. Doll, Hongbo Cong, Yalin Dong, Chang Ye
      Abstract: In this study, an innovative process, electrically assisted ultrasonic nanocrystal surface modification (EA-UNSM), is used to process Ti6Al4V alloy. As compared with traditional UNSM, EA-UNSM results in lower dislocation density and larger grains due to the thermal annealing effect caused by resistive heating. In addition, deeper plastic deformation layer is observed in the electrically assisted case. By supplying mechanical energy and thermal energy simultaneously, a strong dynamic precipitation effect is induced, which generates nanoscale precipitates in the EA-UNSM-treated Ti6Al4V alloy. These nanoscale precipitates can effectively pin dislocations during plastic deformation and thus significantly improve the surface hardness.Electrically assisted UNSM (EA-UNSM) takes advantages of high strain rate plastic deformation and dynamic precipitation, producing a unique structure with nanoscale grains and non-uniformly distributed nano-precipitates. It is observed that the pinning effect exerted by the nanoscale precipitates lead to stronger surfaces, though thermal annealing effect results in grain growth during EA-UNSM.
      PubDate: 2017-08-31T06:17:46.272777-05:
      DOI: 10.1002/adem.201700470
       
  • Characterization of Microstructure and Mechanical Properties of
           Mg–Y–Zn Alloys with Respect to Different Content of LPSO Phase
    • Authors: Klaudia Horváth; Daria Drozdenko, Stanislav Daniš, Gerardo Garcés, Kristián Máthis, Shae Kim, Patrik Dobroň
      Abstract: The Mg–Y–Zn alloys with different contents of alloying elements are extruded at an extrusion ratio of 4:1 at 350 °C. The microstructure of the alloys is of an inhomogeneous character showing fine grains produced due to dynamic recrystallization and coarse original grains elongated along the extrusion direction (ED). Moreover, Y and Zn form a long-period stacking-ordered (LPSO) phase whose volume fraction increases with their increasing content in the alloy. All investigated alloys exhibit distinct fiber textures with basal planes oriented parallel to ED. It is seen that increasing content of alloying elements leads to a weaker texture. Compression tests with concurrent acoustic emission (AE) measurements are performed along ED at room temperature and a constant strain rate in order to reveal active deformation mechanisms in the alloys and to relate them to their mechanical properties. The AE response is also discussed with respect to the volume fraction of the LPSO phase.Mg–Y–Zn alloys with a various content of alloying elements and thus a different volume fraction of the LPSO phase are investigated during compression along extrusion direction. Acoustic emission (AE) technique is applied for revealing the influence of the volume fraction of the LSPO phase on active deformation mechanisms. The volume fraction of the LPSO phase increases at the expense of the unrecrystallized grains what leads to suppressing the twinning activity.
      PubDate: 2017-08-31T06:10:35.967631-05:
      DOI: 10.1002/adem.201700396
       
  • High Efficiency Poly(acrylonitrile) Electrospun Nanofiber Membranes for
           Airborne Nanomaterials Filtration
    • Authors: Riyadh Al-Attabi; Ludovic F. Dumée, Lingxue Kong, Jürg A. Schütz, Yosry Morsi
      Abstract: The potential of poly(acrylonitrile) electrospun membranes with tuneable pore size and fiber distributions were investigated for airborne fine-particle filtration for the first time. The impact of solution concentration on final membrane properties are evaluated for the purpose of designing separation materials with higher separation efficiency. The properties of fibers and membranes are investigated systematically: the average pore distribution, as characterized by capillary flow porometry, and thermo-mechanical properties of the mats are found to be dependent on fiber diameter and on specific electrospinning conditions. Filtration efficiency and pressure drop are calculated from measurement of penetration through the membranes using potassium chloride (KCl) aerosol particles ranging from 300 nm to 12 μm diameter. The PAN membranes exhibited separation efficiencies in the range of 73.8–99.78% and a typical quality factor 0.0224 (1 Pa−1) for 12 wt% PAN with nanofibers having a diameter of 858 nm. Concerning air flow rate, the quality factor and filtration efficiency of the electrospun membranes at higher face velocity are much more stable than for commercial membranes. The results suggest that the structure of electrospun membranes is the best for air filtration in terms of filtration stability at high air flow rate.This work investigates the fabrication of poly(acrylonitrile) (PAN) electrospun structures by varying the fiber diameter to offer specific pore size distributions and fiber morphologies for the capture of aerosol fine particles. The influence of the fiber diameter and membrane properties on the pressure drop and penetration depth of the particles is systematically evaluated. The PAN membranes exhibit separation efficiencies in the range of 73.8 to 99.78% and quality factors up to 0.024546 (1 Pa−1) for uniform nanofiber membranes made from 12 wt% PAN solution having an average fiber diameter of 858 nm.
      PubDate: 2017-08-29T11:28:26.629843-05:
      DOI: 10.1002/adem.201700572
       
  • Effect of Initial Annealing Temperature on Microstructural Development and
           Microhardness in High-Purity Copper Processed by High-Pressure Torsion
    • Authors: Saleh N. Alhajeri; Abdulla I. Almazrouee, Khaled J. Al-Fadhalah, Terence G. Langdon
      Abstract: The effect of the initial annealing temperature on the evolution of microstructure and microhardness in high purity OFHC Cu is investigated after processing by HPT. Disks of Cu are annealed for 1 h at two different annealing temperatures, 400 and 800 °C, and then processed by HPT at room temperature under a pressure of 6.0 GPa for 1/4, 1/2, 1, 5, and 10 turns. Samples are stored for 6 months after HPT processing to examine the self-annealing effects. Electron backscattered diffraction (EBSD) measurements are recorded for each disk at three positions: center, mid-radius, and near edge. Microhardness measurements are also recorded along the diameters of each disk. Both alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing with a clear delay in the onset of softening in the alloy initially annealed at 800 °C. This delay is due to the relatively larger initial grain size compared to the alloy initially annealed at 400 °C. The final microstructures consist of homogeneous fine grains having average sizes of ≈0.28 and ≈0.34 µm for the alloys initially annealed at 400 and 800 °C, respectively. A new model is proposed to describe the behavior of the hardness evolution by HPT in high purity OFHC Cu.The effect of the initial annealing temperature on the evolution of microstructure and microhardness in Cu is investigated after processing by HPT. Copper alloys show rapid hardening and then strain softening in the very early stages of straining due to self-annealing. The final microstructures consist of homogeneous fine grains.
      PubDate: 2017-08-29T03:16:15.769868-05:
      DOI: 10.1002/adem.201700503
       
  • Effects of Cu on Microstructures, Mechanical, and Magnetic Properties of
           Fe–Ni–P Alloys Fabricated by Liquid Phase Sintering
    • Authors: Runjian Jiang; Yang Hu, Guodong Cui, Chengsong Zhang, Ai Li
      Abstract: The Fe–Ni–P–Cu alloys with different copper content (0, 0.5, 1, and 2 wt%) are fabricated by liquid phase sintering (LPS) at 950 °C. The nano-Cu powder is mechanically mixed for 90 min with Fe–Ni–P composite powder using the ethanol as the medium. The microstructure, microhardness and compressive properties of Fe–Ni–P–Cu alloys are investigated. The results indicate that the copper is beneficial to improve the mechanical properties of sintered specimens. The sample contains a small amount of γ-(Fe, Ni) phase when the copper content is 1 wt%, which results in its the highest compressive yield strength (948.1 MPa). The highest microhardness of 371 HV is accessible in Fe–Ni–P–Cu alloy with 2 wt% Cu. The fracture surface analysis indicates that sintered specimens with Cu addition exhibit a typical intergranular mode.Fe–Ni–P–Cu alloys are prepared by liquid phase sintering of Ni–P coated iron and Cu powders. Cu addition improves the hardness and compressive yield strength of Fe–Ni–P–Cu alloy. The alloy with 1 wt% Cu has the highest compressive property and magnetic property. Decrease on γ-(Fe,Ni) phase content enhances the property of Fe–Ni–P–1 wt% Cu alloy.
      PubDate: 2017-08-25T02:00:32.123541-05:
      DOI: 10.1002/adem.201700404
       
  • A Hierarchically Porous Carbon Fabric for Highly Sensitive Electrochemical
           Sensors
    • Authors: Yuan Jiao; Seong Won Cho, Suyoun Lee, Sang Hoon Kim, Seung-Yeol Jeon, Kahyun Hur, Sun Mi Yoon, Myoung-Woon Moon, Aiying Wang
      Abstract: The hierarchically porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating method of soft templates nested on hard templates. A non-woven fabric coated with a solution of F127/resol has been carbonized for the synthesis of both macro-porous structures of 10–15 µm in diameter having meso-porous carbon structures of 4–6 nm, respectively. After carbonization treatment, not only conductivity is significantly improved, the hierarchically porous carbon also shows superhydrophilicity or water-absorbing nature due to mild hydrophilic material and its dual scale roughness. The porous carbon becomes conductive with resistivity widely tuned from 5.4 × 103 Ωm to 3.1 × 10−3 Ωm by controlling the carbonization temperature. As the increased wettability for organic liquids could lead organic molecules deep into carbonized fabrics, the sensitivity of hierarchically porous carbon fabrics benefits the detection for methanol(CH3OH) or hydrogen peroxide (H2O2). This new design concept of hierarchically porous structures having the multi-functionality of high wettability and conductivity can be highly effective for electroanalytical sensors.Hierarchical porous carbon fabrics with controlled conductivity and hydrophilicity have been fabricated by dual templating. The hydrophilicity and conductivity work synergistically, making the porous carbon material a good candidate for electrochemical sensor.
      PubDate: 2017-08-23T12:35:25.573332-05:
      DOI: 10.1002/adem.201700608
       
  • Durable and Recyclable Superhydrophobic Fabric and Mesh for
           Oil–Water Separation
    • Authors: Shaher Bano; Usama Zulfiqar, Usama Zaheer, Muhammad Awais, Iftikhar Ahmad, Tayyab Subhani
      Abstract: The authors report durable and recyclable nanocomposite superhydrophobic coatings on two different substrates of fabric and mesh as prepared by titania nanoparticles and polydimethysiloxane (PDMS). The felted wool fabric and the steel mesh are initially coated with a thin layer of PDMS, which is followed by the deposition of nanocomposite coating of titania nanoparticles embedded in PDMS. The dual surface modification of two kinds of substrates generates highly hydrophobic surface character, which is retained after durability performance as measured in ultrasonication, sand, and emery paper abrasion tests. Oil–water separation experiments are performed using water mixtures with four oils, that is, n-hexane, toluene, kerosene, and diesel to ensure the industrial applications of prepared composite materials. Moreover, nanocomposite coatings are tested for several cycles of oil–water separation in harsh conditions such as hot water, sodium chloride, and hydrochloric acid. The adopted approach improves the separation performance by inducing durability of the prepared nanocomposite coatings along with introducing recyclable character.Durable, recyclable, and superhydrophobic nanocomposite coatings are prepared on fabric and steel mesh. The coatings comprise titania nanoparticles and polydimethylsiloxane (PDMS). The substrates are initially coated with PDMS, followed by deposition of titania/PDMS nanocomposite coating. The resulting highly hydrophobic materials are utilized for the separation of oil–water mixtures.
      PubDate: 2017-08-21T03:16:12.906094-05:
      DOI: 10.1002/adem.201700460
       
  • Ag@Sn Core-Shell Powder Preform with a High Re-Melting Temperature for
           High-Temperature Power Devices Packaging
    • Authors: Fuwen Yu; Bin Wang, Qiang Guo, Xin Ma, Mingyu Li, Hongtao Chen
      Abstract: In this paper, the authors propose a highly conductive die attach material based on Ag@Sn powder for power devices operating at high temperatures or in other harsh environments. The preform can be reflowed at 250 °C (18 °C above the Tm of Sn, 232 °C), but the resulting bondline can sustain high temperatures up to 400 °C with a high shear strength due to the high re-melting temperature of the formed Ag3Sn (Tm = 480 °C) after the complete consumption of the outer Sn layers. In addition, the formed bondline exhibits excellent electrical and thermal conductivities due to the embedded Ag particles in the interconnections. The interconnections also exhibit excellent reliability under thermal shock cycling from −55 to 200 °C because of the increased bondline thickness and inherent ductility of the Ag particles embedded in the Ag3Sn.Ag@Sn Core-shell Powder Preforms is successfully prepared, the preforms required only a short time (5 min) reflow processing at 250 °C, but the resulting interconnections can withstand a high temperature up to 480 °C and exhibit excellent electrical and thermal conductivities due to the high density and the embedded Ag particles in the interconnections.
      PubDate: 2017-08-17T08:00:42.206592-05:
      DOI: 10.1002/adem.201700524
       
  • Effect of Creep and Aging on the Precipitation Kinetics of an Al–Cu
           Alloy after One Pass of ECAP
    • Authors: Markus Härtel; Philipp Frint, Kevin G. Abstoss, Martin F.-X. Wagner
      Abstract: Recent work shows that severe plastic deformation processes such as ECAP or HPT considerably accelerate the precipitation kinetics of Al-Cu alloys. In this study, the authors analyze how a combination of mechanical load, aging time (and increased plastic strain), and aging temperature affects the precipitation kinetics of an AA2017 alloy after ECAP. After solution annealing, the material is processed by one pass of ECAP (120°-channel angle) at 140 °C. Compressive creep tests are performed on the initial condition and the ECAP-deformed material. The resulting microstructures are studied in detail using electron microscopy. To investigate the influence of mechanical loading, interrupted compressive creep tests are performed and compared with aged samples (produced without any mechanical loading at the same temperature and after the same amount of time). By keeping time and load constant in another set of interrupted compressive creep tests, the influence of temperature is investigated. Our study shows that increasing mechanical loading further accelerates the precipitation kinetics. Temperature accelerates the precipitation kinetics as well, but results in coarser precipitates. The authors also find that different creep strains can lead to the formation of two different regions in the microstructure: regions with only a few coarsened θ-phase precipitates, and regions with numerous, finely dispersed precipitates.The authors analyze how a combination of mechanical load, aging time, and temperature affects the precipitation kinetics of AA2017 after ECAP. The authors find that different creep strains lead to the formation of two different regions in the microstructure: regions (A) with only a few coarsened θ-phase precipitates, and regions (B) with numerous, finely dispersed precipitates.
      PubDate: 2017-08-17T07:50:41.475951-05:
      DOI: 10.1002/adem.201700307
       
  • Influence of Ultrafine-Grained Layer on Gaseous Nitriding of Large-Sized
           Titanium Plate
    • Authors: Quantong Yao; Jian Sun, Guanglan Zhang, Weiping Tong, Liang Zuo
      Abstract: In this paper, mechanical shot blasting on a large sized titanium plate is conducted to induce severe plastic deformation, which generates an ultrafine-grained surface layer. The effect of an ultrafine-grained layer on nitriding is evaluated at nitriding temperatures from 600 to 850 °C. The structural phases and mechanical property improvements are investigated and compared to those of a coarse-grained specimen by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and mechanical property measurements. The results indicate that an ultrafine-grained layer enhances the nitriding kinetics and produces a thicker nitrided layer than that of a coarse-grained plate at the same gaseous nitriding temperatures. The improved kinetics are attributed to a greater number of grain boundaries and defects introduced into the titanium plate surface by the mechanical shot blasting treatment. Meanwhile, the surface and cross-sectional hardness values improve compared to the coarse-grained plate due to the thicker nitrided layer resulting from deeper nitrogen diffusion.The authors firstly investigat the effect of ultrafine-grained layer on gaseous nitriding of large titanium plate. The results show that the nitrided thickness of the ultrafine-grained plate is thicker than that of the coarse-grained plate at each nitriding temperature, and the greatest difference between the MSB treated and coarse-grained plates occur at 750 °C.
      PubDate: 2017-08-15T02:41:09.106979-05:
      DOI: 10.1002/adem.201700455
       
  • Superplastic Property of the Ti–6Al–4V Alloy with Ultrafine-Grained
           Heterogeneous Microstructure
    • Authors: Hiroaki Matsumoto; Takuro Nishihara, Vincent Velay, Vanessa Vidal
      Abstract: Ti–6Al–4V alloy having a heterogeneous microstructure composed of ultrafine-equiaxed-α-grains and fine-lamellar-α-grains is investigated for microstructural changes during superplastic deformation at temperature of 700 °C. The Ti–6Al–4V alloy having an optimum fraction of fine-lamellar-α-grains exhibits an excellent superplastic property and the highest elongation of 583% (tested at 700 °C 10−3 s−1). This is mainly due to the optimized activation of grain-boundary-sliding and additional accommodation mechanism associated with frequent occurrences of dynamic recrystallization and β precipitation at boundaries during deformation of the heterogeneous starting microstructure. The present result suggests the possibility that optimizing the starting microstructure so as to have an optimum heterogeneous-microstructure serves as an additional stress accommodation mechanism and leads to a large superplastic elongation.The ultrafine-grained Ti–6Al–4V alloy having an optimum fraction of highly-elongated-α-grains exhibits the highest tensile elongation of 583% (tested at 700 °C 10–3 s–1). This is mainly due to the optimized activation of grain-boundary-sliding and additional accommodation mechanism associated with frequent occurrences of dynamic recrystallization and β precipitation at boundaries during deformation of the heterogeneous starting microstructure.
      PubDate: 2017-08-08T07:01:17.099619-05:
      DOI: 10.1002/adem.201700317
       
 
 
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